b'GarnetFeatureFigure 8.Gemmy alluvial pyropealmandine garnets (up to 15 mm lateral dimension) from Horse Gully, New England region NSW. These pebbly rough garnets are believed to have been shed from a volcanic host, possibly from a basic breccia pipe (top). Faceted pyropealmandine garnets from Horse Gully (bottom) Specimens and photos R. Coenraads in: Webb & Sutherland (2002), thanks for facilitating the use of these images here to George Laking of The Mineralogical Society of New South Wales Inc., and Ross Pogson of the Australian Museum.Figure 9.Andradite and demantoid: collector and gem grade andradite softer than and not as heavy as real garnet. But today glasses[Ca Fe 2 (SiO 4 ) 3 ]. The single dark brown red andradite crystal (42mm wide) is a 3are now made with a wide range of colours and propertiescollector grade stone from Mali which could be worth ~ $100 (top) CC BY SA 4.0/ Didier Descouens / https://commons.wikimedia.org/wiki/File:Andradite-ranging from colourless crown (2.30 g/cc) to emerald greenMali.jpg. The substitution of Cr in the andradite imparts a green colour. This rare flint (4.25 g/cc) and some with Mohs hardness approachingvariety of andradite is called demantoidthe most valuable variety of garnet. that of quartz (Anderson & Jobbins, 1992). Nevertheless, oneThe crystal cluster shown (middle) is thought to be from the Ural Mountains in property glass cannot readily mimic is thermal conductivity,Russia and could be worth ~ $1000 Rob Lavinsky, iRocks.comCC-BY-SA-3.0. which for glass is usually low ~ 1 W/mC. Garnets are ratherA batch of small demantoid gem garnets is shown (bottom) CC BY SA 3.0 / Elke inert minerals and their thermal conductivities are not high,Wetzig / as modified / https://commons.wikimedia.org/wiki/File:Demantoid_~3 to 7 W/mC, but they do exceed most glasses. Comparebobrowa_mineralogisches_museum_bonn.jpg. Demantoid gems are rare, very this with quartz, corundum, and diamond with values ~ 12,good specimens rival emeralds in price.25, 125 W/mC respectively [all values approximatethey can vary, a good summary of thermal conductivity values is givenHealing garnetsby Schn (1996)]. Thermal conductivity needle probes are now readily available for diamond testing (Figure 10). TheseMineral crystals and medicine have long been linked by qualitative devices are small and inexpensive. They indicatefolklore. Garnets have some character, but not much charisma. relative thermal conductivity on an illuminated scale (12Nevertheless, these squat, heavy angular stones allegedly have gradations, on the model shown in Figure 10). Diamonds givetherapeutic uses. This belief has persisted from antiquity to the a maximum reading i.e., 12 or off-scale; a piece of glass can bepresent day. Such claims are based on them functioning by skin used as an arbitrary base reference, and a piece of metal, incontact or as objects of meditation.lieu of diamond, to check the highest reading. Garnets, in my experience, illuminate between the third and fifth gradations,Someone presented with, or finding, a garnet may attempt to with quartz, corundum and diamond all giving higheroptimise its lithotherapeutic powers by discharging the stone responses. These small meters are a handy tool in the kit of anyi.e., washing with water or burying it for a while, presumably geoscientist. to dampen or delete malevolent effects. Garnet according to one source is good for gonads, and for arthritis. Another source Many are the chapters of book and numerous are the articlesclaims such benefits as time travel (life regression), dream recall and papers on gem garnets. The interested reader is advisedand realisation, relief of depression, and purification of the blood. to consult them for further information e.g. see GIA (1995) andYet another maintains that garnet is an energy booster, and has Schumann (2006). stabilising power over chaos whether internal or external, and DECEMBER 2021 PREVIEW 70'