b'GarnetFeaturegarnet exploration with a target, say, of 50 million tonnes of mineralised sand containing about 2 million tonnes of recoverable garnet, and possibly other heavy minerals too e.g., ilmenite. The usual suite of near surface geophysical techniques could be applied in indirect exploration i.e., to locate and define subsurface topographical features that could presumably contain garnets e.g., palaeochannels. Magnetics may be of some limited use. Paramagnetic garnets in alluvial drainage or shoreline sediments are often associated with ferrimagnetic magnetite and paramagnetic ilmenite.Pathfinder garnetOver 100 million carats of natural diamond rough are produced each year mainly from Russia, Canada, Southern Africa, and Australia until recently with the closure of the Argyle mine in the East Kimberly region of Western Australia. Natural diamonds are big business and exploration programs for host pipes and Figure 5.Plot of susceptibility against density for 45 test garnets. Data for thealluvials continue in many locations worldwide.45 samples listed in Table 2 are plotted here. The open boxes give the nominal positions for the five main garnets whose paramagnetic susceptibilities areGarnet mapping is carried out in the first stage of diamond pipe based on the Bleil & Petersen (1982) values. The cross plot suggests that densityexploration, prior to the application of detailed geophysical and magnetic susceptibility are useful in characterising garnets. Most of thetechniques. High pressure pyrope and other indicator minerals garnets tested here belong to the almandinepyrope isomorphous mixtureindicate the likelihood of possibly diamondiferous kimberlite series; a few plot in the andraditegrossular field. The two spessartines fromor lamproite pipes occurring somewhere in a drainage network Brazil have the highest susceptibilities of any tested in this batch. Using thisin which such heavy minerals have been mapped. Garnet trails method of plotting, pyrope and grossular with similar densities (~ 3.6 g/c) andcan indicate localities for detailed geological and geophysical low magnetic susceptibilities ( 0) cannot be resolved. However, the Mexican grossulars (#2731) plotting here near the pyrope / grossular reference arefollow up even if a heavy mineral halo around a pipe has not identified as true grossulars by other means (offwhite-yellowish colour, andbeen identified. Figure 6 shows indicator minerals found in a thermal conductivity: grossular exceeds that of reddish garnet (Clark, 1966)). kimberlite exploration program in Wyoming where electrical Table 3.Garnet and quartz (compiled from various sources including Mavko et al, 1998 and Voynick, 2019).Property Garnet Quartz Density g/cc, t/m3 3.584.32 Garnet has higher unit mass and greater momentum in jet2.65blastingMohs hardness (scriber scratch) 77Knoop hardness (diamond1360 820indentation)Pwave velocity m/s 8510 6050Swave velocity m/s 4770 4090Youngs Modulus GPa 242 94Fracture (a key quality) (Sub) conchoidal, uneven best varieties tend to break into blocky angularConchoidal rounds with use, not self-sharpeningfragments that under abrasive stress form new cutting edgesRecyclable Yes, ~ 5 times NoHealth Dust thought to be non-toxic Debilitating silica dust - lung silicosisIndustrial type Mainly almandinepyrope (but with requisite fracture characteristics, not (low temp) quartzall deposits have this)Deposits Garnet grains shed from parent rocks accumulate in palaeochannels,Alluvials and ocean front sands sought for their dunes, beach sands, alluvials, eluvials, flood plains (some hard rock miningangularitycopious desert sands grain shapes too in Adirondacks USA) roundedMines Only a few, in India, China and Australia (WA: ~200 000 t p.a.) Countless extraction sites around the worldProduction worldwide tonnes1 200 000 Refined concentrate sub mm grainsizes 50 000 000 000 Sands of various quality and p.a. grainsizes for many purposes including abrasivesValue $/t (AUD) 800 Milled, graded, bagged 75 Washed truckloadResources Promising StretchedProspects Excellent opportunities for increased production, garnet will neverSands of the favoured angularity & grain size getting replace quartz sand but demand is there, because it is the best quality,harder to find but large tonnages available in the natural abrasive foreseeable futureExploration for deposits Indirect, in garnet terrain: resistivity, seismic refraction, magneticsDirect, airborne imagery for drainage systems (recent (both magnetite and ilmenite likely to be present), to map favourableand palaeo), then sampling and drillingsubsurface topography, then drillingDECEMBER 2021 PREVIEW 68'