GAIA 1 GAIA GJ HMcCall, Cirencester, Gloucester,UK globe as an integrated system, with the atmosphere, theseas,therivers,andtherocksinteractingtomodu- (cid:1)2005,ElsevierLtd.AllRightsReserved. latetheplanet’sphysicalstateandthustheenvironment inwhichlifecanexist,withthepresenceoflifecontrib- Introduction utingsignificantlytotheinteractions.Gaiaisthusnota synonym of ‘biosphere’ or ‘biota’: it is a much larger TheGaiaconcepthasevolvedinthe30yearssinceit entity.Whenthe Gaiamodelwasoriginallyproposed wasfirstintroducedbyJamesLovelock,anindepend- in the 1970s, it was considered that the atmosphere, ent scientist and inventor. It was initially a rather oceans, climate, and crust of Earth were regulated to vague model relating to the climate and diversity of maintainacomfortablestateforlifetoexist,byandfor theplanetEarth,thoughlivingorganismswerecritical the biota. Temperature, oxidation state, acidity, and to it. The workings of the model were initially un- certain aspects of the rocks and waters were kept, at specified.Theconcept,however,wasoneofa‘super- anytime,constant,maintainedinhomeostasis,bythe organism’operatingto‘regulate’theplanet,especially organismsatEarth’ssurface.Thisconceptisnowseen itssurfacetemperature,yetlackingthe‘foresight’pos- to have been incorrect, because both life, which is sessed by intelligent animals. Lovelock updated his continually evolving, and the geological environment work in 2000, publishing The Ages of Gaia. The are in a state of constant change, and the conditions discussion here is based on this later book, and it is needed to maintain life change very rapidly, with the quiteunavoidabletoechomuchofwhatLovelockhas changingneedsofthebiota,sohomeostasiscannotbe said,becauseheistheonlyanddefinitivesource. maintained for more than very brief periods in Earth history.TheEarthisthusseenasbeinglikeahelicopter, Gaia in the Twenty-First Century which is, unlike a fixed-wing plane, never in stable flight. The changing and evolving needs of the biota Gaia is essentially about life, because life is seen to requirethatthebriefperiodsofhomeostasisarequickly combinewithinanimateprocessesonEarth,affecting overtakenbynewrequirements.Theconceptnowisof and even regulating the physical state of the bio- asuperorganisminwhichtheactivefeedbackprocesses sphere. Lovelock found it surprisingly difficult to operate automatically, so that solar energy maintains find a good definition of ‘life’. Of the definitions comfortableconditionsforlife. found in Webster – ‘‘the property of plants and animals (ending in death and distinguishing them from organic matter) which makes it possible Molecular Biology: The Laws of for them to take in food, get energy from it, grow the Universe etc.’’–andinOxford–‘‘thepropertywhichdifferen- tiates a living animal or plant or a living portion of Lovelock regarded the emergence of the science of organic tissue, from dead or non-living matter; the molecular biology – embodied in the information- assemblage of the functional activities by which this processing chemicals that underpin the genetic basis property is manifested’’ – neither is satisfactory, and ofmostlifeonEarth–ashavingtakenlifescienceout thesecond istautologicalintheextreme.Tothefirst ofaroutineclassificatoryanddescriptivepursuitintoa mightbeadded,before‘‘etc.’’,thewords‘‘andmove, new and exciting study ofhow all the componentsin inthecase ofanimals’’.Lovelockadded tohisdefin- lifeare related. Equally important are physiology, the itionoflifethat‘‘livingthingsuseenergydirectlyfrom study of organisms seen holistically, and thermo- theSunandindirectlyfromfood’’(seeOriginofLife). dynamics, a branch of physics dealing with time and There is no difficulty in accepting that advanced energy,connectinglivingprocesseswithuniversallaws. livinganimalorganisms,suchashumans,aremadeup Two fundamental universal laws of physics are that of intricate communities of connecting cells, and, as (1)energyisconserved,howevermuchitisdispersed, LynnMargolishasshown,thatcellsarederivedfrom and(2)energyisalwaysabating.Hotobjectscool,but micro-organismsthatoncelivedfree(seePrecambrian: coolobjectsdonotheatupspontaneously;waterflows ProkaryoteFossils;EukaryoteFossils).Largerentities, downhill,butnotuphill.Onceused,energycannotbe suchasecosystems,arealsoaccepted,andspaceexplor- recovered.Naturalprocessesalwaysmovetowardsan ationhascontributedtothisunderstandingbyallowing increase in disorder, which is measured by entropy; the entire planet Earth to be viewed from space. The entropy expresses the tendency to burn out. Looking Gaia concept likewise involves envisaging the entire attherelationshipbetweenlifeandentropy,Lovelock 2 GAIA referredtoErwinSchro¨dinger’sconclusionthatlifehas their own destiny in an interesting and complex, but theabilitytomoveupstreamagainsttheflowoftime, comprehensible,way.Thusthesumtotalofthephys- apparently paradoxically and contrary to the second ical state of a planet, with life, is a combination universal law. In fact, what is operating is a tightly oftheinanimateprocessesandtheeffectsoflifeitself. coupled system to favour survival; energy is taken in JZ Young said that the entity that is maintained (e.g., oxygen from the atmosphere is breathed), con- intact, and of which we all form part, is the whole verted (e.g., stored body fats and sugars are trans- of life on the planet. This statement really provided formed),andthenexcreted(e.g.,wasteproductssuch the link between theory and consensus, on the one as carbon dioxide are released back into the atmos- hand,andGaiaconcept,ontheother,expressingasit phere). If the entropy of excretion is larger than the does the view that the entire spectrum of life on the entropyoftheoxygenconsumed,lifecontinues,despite planet has to be considered alongside the geological theseconduniversallaw. andinanimatephysicalprocesses,ifwearetounder- stand how the planet works. This, of course, has led to the present preoccupation in educational circles The Superorganism Concept with ‘Earth System Science’ (see Earth System Sci- There is difficulty in envisaging an eruptive planet ence). Gaia goes further than Earth System Science, withamoltencoreandothercomplexinorganicpro- which is purely a holistic educational approach, in cessesasalivingsuperorganism.However,theinspir- requiring a global system that has the capacity to ing‘whole-planet’imageofEarthasseenfromspace regulate the temperature and composition of Earth’s and the contrast between the environment on Earth surface, hydrosphere, and atmosphere, keeping it andtheenvironmentsonthemoon,Mars,Venus,and comfortableforlivingorganisms. Mercury have focused research on considering how thesignificantplanetarydifferencesarose,andinpar- Criticism of the Gaia Concept ticular on the question of how and why the atmos- pheres differ. The atmospheres of the Moon, Mars, CriticismoftheGaiaconcept,onceadvanced,wasby Venus, and Mercury are a good starting point for no means slight, and the Gaia model was not taken comparisons to Earth, because the atmospheres are seriously by scientists, at all, until the early 1970s. the least complex and most accessible of the zones FredDoolittlecameoutwiththebeliefthat‘‘molecu- of all these planets; indeed, the atmospheric com- lar biology could never lead to altruism on a global positions on other planets were known before space scale’’–altruismbylivingorganismsbeingapparently exploration commenced (see Solar System: Mars; inherent to the concept. Richard Dawkins in 1982 Moon;Mercury;Venus). supported him: ‘‘the selfish interests of living cells TheEarthhasanatmosphereofNandO,withtraces couldnotbeexpressedatthedistanceoftheplanet’’. ofcarbondioxide,methane,andnitrousoxide,notin ItwasalsoremarkedthatGaialackedafirmtheoret- equilibrium, whereas the atmospheres of Mars and ical basis. Heinrich D Holland considered that biota Venus are dominated by carbon dioxide and are in simply react to change in the state of Earth’s near- equilibrium. If the atmospheres of Mars and Venus surfaceenvironmentandprocesses,geologicallypro- wereheated,therewouldbenoreactionwiththesur- duced,andthosethatadaptbettersurvive:therestdo face materials, whereas heating Earth’s atmosphere not. Many scientists saw Gaia as a teleological con- wouldproducereactionsleadingtoacarbondioxide- cept, requiring foresight and planning by organisms, dominated atmosphere. Lovelock concluded that the something that the model surely never represented. improbableatmosphereofEarth‘‘revealstheinvisible However, a major step was taken at the Chapman hand of life’’. The atmosphere contains oxygen and conference of the American Geophysical Union in methane, which should react to form water vapour 1988,whennumerouspapersonGaiawerepresented: andcarbondioxide:thatthisdoesnotoccur,andthat the question of the scientific testability of the Gaia constant atmospheric compositions of these gases are hypothesiswasraised. maintained, reveal, Lovelock believes, that there is Holland’s statement was really an oversimplifica- regulationbylife(seeAtmosphereEvolution). tion,becausetheenvironmentalconstraintstowhich Scientists as early as Eduard Suess and Vladimir an organism adapts can in no way be entirely inor- Vernadsky accepted that there was continuous inter- ganic in origin – geological processes are a combin- action between soils, rocks, oceans, lakes, rivers, the ation of the inorganic and the organic. Lovelock atmosphere,and life.Muchlater,Stephen JayGould stated this when he objected that ‘‘life cannot have stated that ‘‘organisms are not billiard balls, struck adapted solely to an inert world determined by the in a deterministic fashion and rolling to optimal dead hand of chemistry and physics’’. The two main positions on life’s table’’. Living things influence objections to Gaia were, first, the teleological one GAIA 3 (forecast or clairvoyance seemed to be needed for Gaia tobe true) and, second, thefact that ecological regulationbylifecouldonlybepartial.Whatmustbe operatingisacombinationofregulationbytheliving and the inorganic, even though in the long term, a wholly inorganic interference, such as an asteroidal impact, would be reacted to by the biota, much of it bydyingoff.However,someofthebiotamaysurvive, regeneratingandexpandingtoagainaffectthephys- icalenvironmentofthelifeformscontinuingtoexist atornearthesurface. Other objections to the Gaia concept have been a creationist argument, based on Schro¨dinger’s conclu- sionson‘life’,thatsomeorganismsdonotneedthesun, Figure 1 Regulation by white daisies. The helmet-shaped andalsoasuggestionthatLovelock’simageofEarthas curve(B)depictstheresponseofdaisiestotemperature.Curves a‘spaceship’ignoresthefactthat40000tonnesyear(cid:1)1 AandA1depicttheresponsesofplanetarytemperaturetothe areacoveredbydaisies,curveA1beingforalowerheatinputby ofextraterrestrialdustentersEarth’satmosphereand theplanet’sstar.Intheabsenceofdaisies,thechangeinplanet- isdepositedonEarth’ssurface. ary temperature (DT) would be nearly 15(cid:2)C, whereas in their presence DT is only about 3(cid:2)C. Reproduced with permission fromLovelockJ(2000) The Ages of GAIA: A Biography of Our Living Lovelock’s Hypothesis Earth.Oxford:OxfordUniversityPress. The‘Daisyworld’Model be determined by the average shade of colour of the Lovelocksawthatheneededasimplemodeltoillus- daisy coverage. If the average is the dark colour trate his point. The effect of snow cover on the shade, the albedo is low, more heat is absorbed, and ground,apurelyinorganicchange,hadalreadybeen thesurfaceiswarmed;iftheaverageisthelightshade, modelledtoshowhowsnowcoverchangesthealbedo 70–80%ofheatisreflectedandthesurfaceiscolder. and thus the cooling in the atmosphere. Lovelock In the scale 0–1, dark daisies will have an albedo of, developed a simple model, the ‘Daisyworld’ model, say,0.2;lightdaiseswillhaveanalbedoof0.7andthe illustratingthewaylifecouldhaveasimilareffect. bare ground, 0.4. The initial weak Sun will increase TheDaisyworldparableof1982proposesaplanet until 5(cid:2)C is attained and that will favour the dark like Earth in size, mass, and orbital distance from daisies, because they have greater absorption of sun- a star that is like Earth’s sun in mass and density; light and will warm up the temperature just beyond like Earth’s Sun, the Daisyworld Sun increases its 5(cid:2)C.Thelightdaisieswillbedisadvantagedandwill output as it ages (the nature of the H/He reaction fadeanddie.Nextseason,therewillbemoreseedsof meansthatourSunwas30%cooleratitsbeginning, thedarkstrainanditwillbecomewarmerandsoon, butwilleventuallyheatupsoastoconsumeMercury, until most of the planet is colonized by the dark Venus, and possibly Earth). The Daisyworld planet strain.However,whentheupperlimittemperatureis has more land than sea, compared to Earth, is well approached, the light strain, because of their high watered, and plants can grow anywhere on the land albedo, will keep the temperature in check and so surface if the climate is right. The sole plant is a will take over from the dark strain. The growth of daisy, which may be dark, neutral, or light in colour the star’s heat flux will eventually be so great that shade.Asingleparameter,variabletemperature,con- nothing can keep the temperature below 40(cid:2)C and trolswhetherthedaisycangrow–5(cid:2)Cisthegrowth all the daisies will die off. Flower power will no threshold, 20(cid:2)C is the optimum, and 40(cid:2)C is the longer be enough. The planet will be barren and upper limit. The mean temperatureof the planet isa there will be no way back. Figure 1 reproduces simple balance between the heat received from the Lovelock’s most important Daisyworld diagram. sun and the heat lost to the cold depths of space in The Daisyworld parable was devised to counter the the form of long-wave radiation. The complication ‘teleological’criticism. on the real Earth of reflection upwards and blanket- ing downwards of heat by clouds is avoided, by TheFourComponentsofGaia havingalltherainfallontheDaisyworldplanetoccur at night and having no clouds present in daytime. Lovelock described Gaia as an automatic, non- Thereisjustenoughcarbondioxideintheatmosphere purposeful, goal-seeking system, and considered it for the plants to grow. The mean temperature will tobemadeupoffourcomponents: 4 GAIA 1. Living organisms that grow freely, exploiting any remain possibilities of abrupt extinction of life on environmentalopportunitiesthatopenup. Earth through physical disasters. For example, the 2. OrganismsthataresubjecttotherulesofDarwin- entire planetary biota might have been extinguished ian natural selection: the species that leave the in the latest Proterozoic; if glaciation, a complex mostprogenysurvive. phenomenon attributed to Milankovitch cycles in 3. Organisms that affect their physical and chemical theSolarSystem,hadcoveredtheglobeinthe‘snow- environment.Thus,animalschangetheatmosphere ball Earth’ episode, it might well have extinguished by breathing, taking in oxygen and breathing out all life. Definition 2 begs the question, ‘‘what about carbondioxide.Plantsandalgaedothereverse.In the long early period in the Archaean, when only numerousways,allformsoflifeincessantlymodify very primitive forms of unicellular life apparently thephysicalandchemicalenvironment. existed?’’Theplanetinfactgotonverywellthrough 4. Theexistenceofconstraintsorboundsthatestab- a vast period of time when it was only partially in- lishthelimitsoflife.Itcanbetoohotortoocold; habited by life, and that being very primitive, com- there is a comfortable warmth in between, the pared with now. Regarding definition 3, surely to preferred state. It can be too acid or alkaline; the word ‘rocks’ the words ‘hydrosphere and bio- neutrality is preferred. For almost all chemicals, sphere’should be added. Finally, in definition 4, the there is a range tolerated or needed by life. For statement that ‘‘increased diversity leads to better many elements, such as iodine, selenium, or iron, regulation’’ is questionable. The evidence for this too much is a poison and too little causes starva- does not seem to be to be given by Lovelock: the tion. Pure, uncontaminated water will support word ‘regulation’, which is fundamental to Gaia little, but neither will the saturated brine of the concept,seemstobeaproblem.Theconceptappears DeadSea. to be tantamount to accidental regulation: in the realworld,asopposedtotheDaisyworld,thereality would seem to be that the biota make a major con- DefinitionsandCriticisms tribution to the physical and chemical environment Lovelockadvancedasetofdefinitions: of the biosphere, and that, throughout Earth history since life appeared on the planet, the bounds of liv- 1. Life is a planetary phenomenon with a cosmo- ability of the planetary biota as whole have never logicallifespan.Onthisscale,itisnearlyimmortal beenexceeded,despiteseveralmassextinctions–yet andhasnoneedtoreproduce. total extinction could happen at any time. Also, like 2. There can be no partial occupation of the planet the inorganic physical and chemical (geological) bylivingorganisms.Suchaconditionwouldbeas changes,changesinducedbythebiotacanbebenign impermanent as half an animal. Ineluctable phys- or adverse. The biota can react to change to counter ical and chemical forces would soon render (the adverse changes; initially benign changes can lead planet)uninhabitable.Thepresenceofasufficient to adverse changes in the long run (e.g., overpop- numberofanimalsontheplanetisneededforthe ulation). There is no law of the sum total planetary regulationoftheenvironment. biota adjusting to regulate the environment, keeping 3. Our interpretation of Darwin’s great vision is within bounds, but so far (luck?), the bounds have altered. Gaia draws attention to the fallacy of the not been overridden in the case of the overall biota, concept of adaptation. It is no longer sufficient to not at any time in geological history, since life first saythat‘‘organismsbetteradaptedthanothersare appeared. likelytoleaveoffspring’’.Itisnecessarytoaddthat thegrowthoftheorganismaffectsitsphysicaland Gaia and the Geological Record chemicalenvironment;theevolutionofthespecies and,therefore,theevolutionoftherocksaretightly Lovelock, in his second book, considered Gaia in coupledinasingle,indivisibleprocess. terms of the geological record, discussing the Ar- 4. Theoretical ecology is enlarged. By taking the chaean, the Middle Ages, and the contemporary species and the physical environment together as environment. Before concluding, it seems apposite a single system, we can, for the first time, build to refer to a recent contribution to the discussion by ecological models that are mathematically stable, EuanNisbet. andyetincludelargenumbersofcompetingspecies. In these models, increased diversity among the Nisbet’sEssay speciesleadstobetterregulation. EuanNisbet,inawide-rangingFermorLecturetothe There are criticisms of Lovelock’s definitions. Of Geological Society in 2002, explored the question definition 1, it is perhaps better to admit that there whether the presence of life or inorganic processes GAIA 5 had constituted the dominant factor in shaping the the global biota.One cannotescape thefact that the physicaldevelopmentandincontrollingthephysical physical state of the near-surface zones of the planet conditions at or near Earth’s surface since life ap- has, for more than 3500 million years, been suffi- peared on the planet more than 3500 million years ciently benign for some life to continue to exist; ago. He found that life had a dominant role in throughoutthedevelopmentoflife,fromprotozoans controlling the condition of the atmosphere through to destructive humans, the physical state of Earth’s this immensely long period, and that, in turn, the surfacehasneverledtoextinctionofthesumtotalof surface temperature had a very significant control lifeontheplanet.Yetthehistoryhassurelybeenone on the tectonic evolution, especially plate tectonics. of reactions by life to changes, including extremely Evenso,Nisbetcouldnotruleastowhichprocesses, criticalsituations,bothinorganicallyandorganically biological or inorganic, had been the dominant triggered; changes have never reached the point of factor – the two kinds of processes had operated driving life over the edge to extinction, but even so, together to control the physical conditions. That this is not regulation, because there is no rule in- life had exerted a significant effect on the ongoing volved. The irretrievable end-point situation has just physicalevolutioncouldnotbearguedagainst. not happened. In fairness to Lovelock, in his 1991 Nisbet based his conclusions on inorganic and or- book he did include a chapter entitled ‘‘The People ganic models, and in them not all the assumptions Plague’’, inwhich heargued that humans, having no made are necessarily correct. For instance, Nisbet predators, had in effect become a plague on the tended to extend plate tectonics back through the planet, and could well take the life on the planet to Archaean,whereastherearestrongargumentsagainst that irretrievable end-point situation. Of course, one this (e.g., see the publications by Hamilton in 1998, by could argue that humans do have predators, even if Bleeker in 2002, and by McCall in 2003). Considering minute ones – viruses and microbes that could blot the real world, rather than models, Nisbet could not them out forever and leave behind an Earth smiling decide which had beenin the driving seat,and he be- with other life forms, until the Sun fulfils its destiny lievedthatthequestionwaspossiblynotquantifiable. andincineratestheplanet. The atmosphere was,however, largely the product of Theinfluenceoftheexistenceoflifeonthephysics theexistenceoflifeatornearEarth’ssurface. andchemistrynearthesurfaceoftheplanet,andthe feedback to life from that – the essence of Gaia – is well understood, but has obviously become more Beyond Gaia complexasthespectrumoflifeonEarthhasbecome Gaia,attheleast,isabrilliantconcept,andLovelock more complex, starting with the primitive prokary- has provided a stimulating basis for looking at otes in the Early Archaean. For example, a plant the entire globe and for integration of the effects of population limited to algae must have left bare rock theprogressivedevelopmentoflifeandpurelyinani- surfacesintheArchaean,whereasoncehigherplants mategeologicaldevelopmentthroughtime.Thiscon- appeared, there must have been a much more com- cept also encompasses the maintenance throughout plex reaction of the land surface to the Sun’s radi- timeofconditionssuitableforlifetocontinuetoexist ation. In fact, these relationships, though complex throughout3500millionormoreyears.However,at and possibly unquantifiable at the present state of this minimal assessment, it is no more than Earth the planet, are less obscure than are other processes. SystemScienceunderanothername,butemphasizing Forexample,howdoesananimalobtaininformation thespecialcontributionoflifetothechangingstateof that another animal exists and has a character or the atmosphere, hydrosphere, and geological pro- activitytowhichthefirstanimalcanadapt,toobtain cesses, which in sum determine the physical condi- benefit? How does the information get into the gen- tions under which life of some sort can continue to etic process? The present author, in an unpublished ‘operate’.TheGaiaconcept,however,isclaimedtobe work, The Vendian (Ediacaran) in the Geological more than this, and the critical word is ‘regulate’. Record, has called this mysterious process ‘cogni- Lovelock never intended Gaia to have a teleological zance’. An example of this is the case of eoforamini- significance, but even so, to regulate something fera found in Uruguay, in latest Proterozoic rocks. wouldseemtoimplyanelementofdesign.Itmaybe These organisms agglutinated fine mineral particles that when an extreme condition occurs, such as an on theirsurface, and it has been glibly said that they extreme greenhouse condition (Cretaceous) or a did this to make themselves less palatable to preda- ‘snowball Earth’ approximation (end Proterozoic), tors. But how did they know that their mates were the reactions of the living plant and animal popula- beingeaten?Itwouldseemthatthisaspectofgenetics tionsthatsurvivemaybebeneficial,butequallythey is what scientists should now be concentrating on, couldactuallybeadverseandeliminateevenmoreof ratherthan‘regulation’bythesumtotalbiota. 6 GEMSTONES See Also Lovelock J (1978) GAIA: A New Look at Life on Earth. Oxford:OxfordUniversityPress. Atmosphere Evolution. Biodiversity. Earth Structure LovelockJ(1991)GAIA:ThePracticalScienceofPlanetary andOrigins.EarthSystemScience.Evolution.Origin Medicine.London:GaiaBooks. of Life. Palaeoclimates. Precambrian: Eukaryote LovelockJ(2000)TheAgesofGAIA:ABiographyofOur Fossils;ProkaryoteFossils.Solar System:Mars;Moon; LivingEarth.Oxford:OxfordUniversityPress. Mercury;Venus.TraceFossils. McCall GJH (2003) A critique of the analogy between Archaean and Phanerozoic tectonics based on regional Further Reading mapping of the Mesozoic–Cenozoic plate convergent zone on the Makran, Iran. Precambrian Research BleekerW(2002)Archaeantectonics–areview.In:Fowler 127(1-3):5–17. CMR,EbingerCJ,andHawkesworthCJ(eds.)TheEarly Myers N (1984) Gaia: An Atlas of Planet Management. Earth: Physical, Chemical and Biological Development. NewYork:Doubleday. Special Publications 199, pp. 151–181. London: Geo- Nisbet E (2002) The influence of life on the face of the logicalSociety. Earth. In:Fowler CMR, Ebinger CJ, and Hawkesworth GaucherCandSprechmannP(1999)UpperVendianskel- CJ (eds.) The Early Earth: Physical, Chemical and etal fauna of the Arroyo del Soldado Group, Uruguay. Biological Development. Special Publications 199, pp. Beringeria23:55–91. 275–307.London:GeologicalSociety. Hamilton WB (1998) Archaean magmatism and deform- ationwerenotproductsofplatetectonics.Precambrian Research91:131–175. GEMSTONES COldershaw, St.Albans, UK Quantifying Gemstone Mining (cid:1)2005,ElsevierLtd.AllRightsReserved. While mineral exploration is generally well docu- mented and statistics are available, providing figures for production for most minerals on a country- Introduction by-country basis, this is generally not the case with There are almost 4000 minerals known, of which gemstones (except perhaps for diamonds), which only about 50 are commonly used as gemstones. have always been difficult to quantify. Much gem- Thosethatformcrystalsofsufficientsizeandquality stone mining is carried out in remote places, with to be cut and fashioned as gems are referred to as secrecy and security to protect the interests (and ‘gem quality’ or ‘cuttable’ pieces; other minerals or sometimes the lives) of the owners (Table 1). In rocks with particularly attractive features (colour, some areas, families or groups of villagers purchase texture,orpattern)maybecalled‘decorative’pieces. alicence tomine;inother areasthere islittle regula- Crystalsareusuallyfaceted(cutandpolished)togive tion,andminingmaybecontrolledbylocalleadersor agemstonewithanumberofflatfaces,whiledecora- warlords, with all the problems associated with tivestonesaremainlytumbledorpolishedtoproduce regionsofconflictandpoliticalunrest. piecesforpersonaladornmentorobjetsd’art. Over large regions it is difficult to assess the pro- Gemstones are formed in each of the three main duction figures for particular gemstones, although rock types: igneous, sedimentary, and metamorphic. general trends in availability and value (which could Miningmethodsdependonthetypeofgemstoneand be as much a product of fashion as of supply) give itsopticalandphysicalqualitiesandonwhetheritis some indication of production figures. On a smaller beingminedfromtherockinwhichitwasformedor scale, a specialist gemstone buyer (such as a ruby retrieved from secondary (placer) deposits produced or sapphire buyer) will, by building relationships byweatheringanderosion. with miners, mine owners, and local traders, gain A study of modern-day gemstone mining and expertise and some knowledge of the volume and retrievalcovers every miningmethod,from the trad- quality of gemstones being mined in that region. itional searches in streams and rivers using a pan As new localities are identified and new gemstones or sieve to the ultra-high technology and research reach the markets, previously known localities or models used in diamond mines deep underground. gemstones may lose their appeal or a region may Ultimately, any source of gemstones will be mined become unproductive – so the market can be quite andexploitedonlyifisfinanciallyviable. changeable. GEMSTONES 7 Table1 Themainlocalitiesofsomeofthebest-knowngemstones(diamond,ruby,sapphire,emerald,aquamarine,chrysoberyl, topaz,tourmaline,peridot,garnet,pearl,opal,spinel,zircon,turquoise,nephritejade,andjadeitejade) USA Egypt Russia Myanmar(formerlyBurma) Aquamarine Emerald Demantoidgarnet Chrysoberyl Emerald Peridot Diamond Jadeitejade Jadeitejade Turquoise Emerald Peridot Nephritejade Nigeria Nephritejade Ruby Peridot Aquamarine Topaz Sapphire Ruby Sapphire Tourmaline Spinel Sapphire Spinel Afghanistan Topaz Topaz Topaz Aquamarine Tourmaline Tourmaline Zaire,Angola,andNamibia Ruby Zircon Turquoise Diamond Spinel Thailand Canada Zambia Pakistan Almandinegarnet Diamond Chrysoberyl Aquamarine Ruby Emerald Emerald Sapphire Nephritejade Botswana Grossulargarnet Zircon Mexico Opal Diamond Ruby China SouthAfrica Spinel Aquamarine Topaz Diamond Topaz Diamond Tourmaline Emerald India Nephritejade Turquoise Peridot Almandinegarnet Peridot Honduras Ruby Aquamarine Ruby Opal Tourmaline Chrysoberyl Sapphire Colombia EastAfrica Diamond Turquoise Emerald Aquamarine Emerald JapanandTaiwan Brazil Diamond Ruby Jadeitejade Chrysoberyl Emerald Sapphire Topaz Diamond Ruby SriLanka Australia Emerald Sapphire Chrysoberyl Diamond Opal Tanzanite Garnet Emerald Topaz Tourmaline Ruby Nephritejade Tourmaline Madagascar Sapphire Opal Germany Aquamarine Spinel Sapphire Topaz Chrysoberyl Topaz NewZealand Italy Topaz Tourmaline Nephritejade Tourmaline Tourmaline Zircon Guatemala FormerCzechoslovakia Jadeitejade Garnet Iran Opal Turquoise Gem-testing laboratories, museums, and specialist gemmological journals such as the Journal of Gem- gemstone collectors are often the first to hear of a mology, Gems and Gemmology, and Australian new find. Some gemstones will be mined in suffi- Gemmologist. cientlylargevolumestoreachthemarketplaceworld- wide, for example tanzanite (the blue variety of the Alluvial and Eluvial Deposits mineral zoisite), which was discovered in 1967 in Tanzania and is now available through many retail Gems formed in igneous or metamorphic rock may outlets.Othersmaybeminedoutfairlyquickly,with be subject to weathering and erosion, breaking most of the gemstones going to a few specialist down the rock and releasing the gemstones (see buyers. Weathering). The gems may remain where they are Some particularly rare finds are found only in or be transported by ice, wind, or water and de- museums or private collections. Other gems are cut posited elsewhere. Eluvial gem deposits are form- for collectors but, because of their rarity or physical ed as a result of the weathering of rock that has properties (for example they may be too soft remained in the same place. Alluvial deposits for everyday wear), do not reach the retail market. are deposited by flowing water (see Sedimentary En- New localities and new gemstone finds of vironments: Alluvial Fans, Alluvial Sediments and interest,suchasaparticularlyfine-colouredgemstone Settings). or a mine that is producing particularly clean large Gemstones are generally harder and heavier than specimens of a gemstone, are usually reported in thesurroundingminerals.Theyarenotcarriedasfar 8 GEMSTONES by flowing water and tend to sink faster, becoming concentrated inpockets orareas along riverbanks or withingravels(gemgravels).Therefore,alluvialgem- stonedepositscontaingemstonesthataresufficiently hardanddurabletowithstandtheconditionswithout breaking, rather than those that are heavily included orpronetofractureorcleavage. Because nature has already partially eliminated theweakerspecimens,thepercentageofgem-quality gemstones in gem gravels is usually high, with the result that more gemstones are retrieved from gem gravels than from any other type of deposit. Alluvial deposits, such as the gem gravels of Sri Lanka and Myanmar (formerly Burma), contain a wide range of gemstones including ruby, sapphire, spinel,chrysoberyl,topaz,tourmaline,andgarnet. Becausegemstonesassociatedwithgemgravelsare often found together, the discovery of one type of gemstone from a gem association (sometimes called a tracer gem) can be used by exploration teams and prospectors to ‘trace’ potential gemstone mining areas. Another technique is to map the courses of ancient river beds or present-day rivers and streams andthenfollowtracergemsdownstreamtofindareas where the gemstones are present in large enough concentrationstoberetrieved. The oldest and most traditional mining methods arestillpracticedinareaswheregemstonesarenear the surface and relatively easy to find and retrieve Figure 1 A lady river panning, washing gravel in search of and where labour is cheap. In Indonesia, Malaysia, chrysoberyl cat’s-eyes (Kerala, India). Printed with permission Sri Lanka, and India, for example, local people fromAlanJobbins. search rivers and streams and excavate the gravels andsedimentsfromnow-buriedriverbeds. RubyandSapphireDeposits Panning for gems works on the principle that the gemsaregenerallyheavierthanthesurroundingmud, TherubiesandsapphiresofThailandandCambodia pebbles, or rock fragments. As the pan of water and are found in alluvial and eluvial gravels, derived sedimentis‘jiggled’,thegemstonessettletowardsthe from highly alkaline basalt (Figure 5). The main bottom of the pan while the lighter constituents and mining area is near the border between Thailand waterarewashedoverthepan’sedge(Figure1).The andCambodia,aroundChantaburi. heavier concentrate may be sieved to separate larger Sri Lanka is a source of alluvial sapphires, which gemsoritmaybespreadoutontablesorclothstobe arederivedfrompegmatiteandgneissandarefound hand-sorted. in a wide range of colours, including the pinkish- Alluvial deposits are generally mined by similar orange padparadscha. Padparadscha is particularly methods wherever they are found in the world, usu- rareandisnamedafterthesinhaleseforlotusflower, ally by digging shafts or pits or by collecting the whosecolouritresembles. alluvium from rivers and streams using sieves and Rubies and sapphires are members of the corun- pans. Dams may be constructed to manage the dumfamily,anddifferenttraceelementswithinthem water flow, and water may be diverted to wash the giverisetothecolourrange.Rubiesarered(coloured gem gravels (Figures 2 and 3). Final sorting is done by chromium and possiblyvanadium); blue sapphire byhand. is coloured by iron and titanium. Other sapphires, Often the mining and retrieval of gems in these such as green sapphire, pink sapphire, and mauve traditional ways is a family project, varying only sapphire, result from the addition of various trace slightly from country to country. The men and boys elements during the gem’s formation. Colourless may work in the rivers or dig the pits, while women (white)sapphirehasthesimplechemicalcomposition andgirlssieveorsortthegems(Figure4). aluminiumoxide(Al O ). 2 3 GEMSTONES 9 Figure 2 A young worker carries the gemstone concen- Figure 3 Washing gemstone concentrate in a small pond tratecalled‘paydirt’or‘rai’in‘Burmese-style’baskets(Pailin, (Pailin,Cambodia).(cid:1)AlanJobbins. Cambodia).(cid:1)AlanJobbins. Thecolourdoes,tosomeextent,affectthemining, therehavebeenfindsofprehistorictoolsthatsuggest as the more popular and valuable colours are thatmininghasbeencarriedoutformanythousands more sought after. It should be noted, however, that ofyears. some gemstones, including corundum, may have Traditional methods involve digging a narrow pit their colour changed or enhanced with heat treat- or vertical shaft, just wide enough for the miner to ment, irradiation (electrons, X-rays, etc.), or other be lowered down to dig out the layer of weathered techniques. metamorphosed crystalline limestone (marble) that Kashmir sapphires, which are famous for their contains the rubies. The miner removes rock (often cornflowercolour,areminedinSanskar,aninhospit- 2–3m below the surface) and placesit in abasket to ablemountainousareaoftencoveredbysnow,north- behauledtothesurfaceandsorted. west of the Himalayas. The sapphires are found in Following the establishment of the Burma Ruby feldspar pegmatites or in gravels derived from the Mine Company in Victorian times, some mining pegmatites.Therehasbeenintermittentminingsince techniques were modernized. Water pumps were the 1920s; however, little is known about present introducedtospeedthewashingprocess,andintricate miningbecauseofthepoliticalsituation. channelswereconstructedfromwoodenplanks,along which water was sluiced to separate the rubies from MogokRubies rockfragments.Asaresultofthecollapseofthemarket The most famous rubies are the ‘pigeon blood’- followingtheintroductionofsyntheticrubiesandsap- coloured rubies from the Mogok Stone Tract area of phiresintheearlytwentiethcentury,theBritishCom- northern Myanmar, about 110km north of Manda- panyfailedandtraditionalmethodswerereintroduced. lay. Documentary evidence shows that mining has Inthe1990snewmineswereestablishedintheMong been carried out since the sixteenth century, but Hsuarea,about250kmeastofMandalay. 10 GEMSTONES Figure4 Girlssortinggemstoneconcentrate(Pailin,Cambodia).(cid:1)AlanJobbins. Gemstones in Igneous Rocks Where rock is harder, picks and drills may be suffi- cient to prise loose the gemstones from the parent rock (the host); otherwise the rock has to be mined, crushed, washed, and sorted to retrieve the gem- stones. Diamonds are mined on a larger scale and with more highly mechanized methods than any othergemstone. ExtrusiveIgneousRocks Alluvialgemdepositsderivedfrombasalticlavashave been mentioned above. The basaltic lavas (extrusive igneous rock, where magma has been erupted from volcanoes as lava) may also be mined. Peridot is commonly formed in basaltic lava. The peridot gen- erallyformsassmallcrystalsorwithinvesicles(small bubbles)andvoidsinthelava.Othergemsthatcrys- tallize from lavas as they cool include zircon, ruby, andsapphire. IntrusiveIgneousRocks Some of the largest crystals form where the magma isnoteruptedbutrisessufficientlyintheEarth’scrust tocoolslowly.Theslowerthecooling,thelargerthe crystals that can form. Igneous rocks formed in this wayaresaidtobeintrusive. Gemsmayformindykes(smalligneousintrusions) intruded into surrounding rocks, which may crop Figure 5 Eluvialworkingsinweathered(decomposed)basalt abovebasaltlava(Pailin,Cambodia).(cid:1)AlanJobbins. out at the surface as a result of weathering. Mining