b'GarnetFeatureReferencesAnderson, B, and E. Jobbins, 1990. Gem Testing: Butterworths, LondonBandy, M C. and J.A. Bandy, 2004. De natura fossilium: Dover Publs. [Agricolas Mineralogy]Bleil. U. and N. Petersen, 1982. Magnetic properties of natural minerals. In: Angenheister, G (Editor), Physical properties of rocks. Landolt-Bornstein numerical data and functional relationships in science and technology, Group V: Geophysics and Space Research, Volume 1b, 305-365, Springer-Verlag. Berlin.Bloss, F.D., 1971. Crystallography and Crystal Chemistry: Holt, Rinehart & WinstonBeckmann, J., 1799. Marbod liber lapidum seu de gemmis, J.C. Dieterich, Gottingen. [Marbods book of stones and on gems, poem no. 23: carbunculus]Caley, E. R. and J.F.C. Richards, 1956. Theophrastus on stones: The Figure 10.Cheap diamond testers give rapid, relative indications of thermalOhio State University.conductivity by a needle point technique. To check whether a material is glassClark, S.P. Jr., 1966. Handbook of Physical Constants. Memoir 97 (paste) or garnet, the tester is set to zero when touching a piece of glass, whichGeol. Soc. America Inc.usually has a very low thermal conductivity, ~1 W/mC. Garnets do not have aDeer, W., Howie, R. and J. Zussman, 1992. An Introduction to the high thermal conductivities, they are low, in the 3-7 W/mC range. The MexicanRock-Forming Minerals: Longman, Pearson Education Limited, grossular (top) give an indication of 3 on the scale, and so, by an easy qualitativeUnited Kingdomthermal measurement, we can say it probably is not glass. Ruby (Al 2 O 3+ Cr)Eicholz, D. E., 1971. Pliny natural history, Book 37, Harvard Uni. sometimes looks like garnet; it has a much higher thermal conductivity, ~25 W/ Press. [Loeb Classical Library #419]mC. The hexagonal prism section of very low-grade pink ruby (bottom) gives anEmerson, D. W., 1990. Notes on mass properties of rocksdensity, indication of 8 on the scale. Diamond (not shown) goes off scale and the meterporosity, permeability: Exploration Geophysics 21:209-216.beeps. Of course, a nice ruby would be preferable to a garnet. Rubys densityGemmological Institute of America, 1995. GIA Gem Reference (~ 4.0 g/cc) is similar to red-brown garnet, but it is much harder (H = 9). However, it is not generally a good idea to hardness test scratch a good quality specimen. Guide: GIA, Santa Monica, Calif.Harris, J.A., 2016. Surgery, the ultimate placebo: Uni. NSW Press. Ltd.ensures survival in crisis or trauma. Garnet is said to release badHausel, W.D., McCallum, M. E. and T.L. Woodzick, 1979. karma and to promote success in lawsuits. Some stone! OnePreliminary report on exploration for diamondiferous could expand on all this, exponentially, but to no real purpose.kimberlites Colorado-Wyoming. Colorado Mining Assoc. Suffice it to say that I think the link to medicine is imaginary, andYearbook: 109-122.if garnet does help a person it is, in my view, a placebo effect (seeHornblower, S. and A. Spawforth, (eds) 2012. The Oxford Classical Harris, 2016). The magic, fantasy and wish list aspects are justDictionary 4th edn: Oxford Uni Presspart of the folkloric litho-therapy show (and not just for garnets). Jenke, G., 1983. The role of geophysics in the discovery of the Ellendale and Fitzroy kimberlites. Abstracts of the Australian Concluding remarks Society of Exploration Geophysicists, Biennial Conference, Brisbane: 66-72.This article has presented some aspects of the history andMavko, G., Mukerji, T. and J. Dvorkin, 1998. The rock physics mineralogy of the garnet. It also discussed physical properties.handbooktools for seismic analysis in porous media: Although pure garnet varieties probably only exist in syntheticCambridge Uni. Press.form, magnetic susceptibilitydensity plots can supply someSchn, J.H., 1996. Physical properties of rocks: Pergamon, Elsevier information on a garnets mixed solid solution composition,Science, Oxfordprovided that ancillary magnetites are not present as inclusions.Schumann, W., 2006. Gemstones of the World: Sterling Publ. Simple thermal measurements may be useful in distinguishingNew Yorkgarnet from paste or other unwanted minerals such as quartz.Smith, C.B., Atkinson, W.J. and E.W.J. Tyler, 1990. Diamond Garnet itself may present some exploration opportunities forexploration in Western Australia, Northern Territory, and the gem and abrasive industries, but it is not a vitally importantSouth Australia. Monograph 17: 434, Australian Institute of economic mineral such as nickel or copper sulphide. The account ofMining and Metallurgy, Parkville, Victoria.garnet given here is by no means a complete narrative. If interestedVoynick, S., 2019. Garnet an industrial commodity: Rock & Gem in a mineral that can show grunt and (sometimes) grace, readers49(4): 56can easily access additional information in the science literature,Voynick, S., 2021. Shakespeares gemstone: Rock & Gem 51(9): and in popular publications (which sometimes lack accuracy). 64-66.Webb, G. and L. Sutherland, 2002. Gemstones of New England Acknowledgements New South Wales: Min. Soc. NSW Inc.David, Lainie, and Samuel Kalnins, and Lisa Emerson are thankedYang, Y. P., and D.W. Emerson, 1997, Electromagnetic for their suggestions and help in preparing this article. conductivities of rock cores, theory and analogue results. Geophysics 62(6):1779-1793.I would like to acknowledge especially the assistance that David Kalnins has provided in the preparation of this paperDon Emerson is a geophysical consultant specialising in and other Preview articles submitted over the last few years. Histhe physics of minerals and rocks, he also has an interest in knowledge, support, advice, and technological expertise haveancient and medieval geoscience. been invaluable.71 PREVIEW DECEMBER 2021'