b'Pyritethe firestoneFeaturePyritethe firestonecoatings on, and fracture fillings in, disseminated pyrite of extremely fine grain size. Australia has many impressive massive pyrite deposits such as those at Mt Lyell, Nairne, Koolyanobbing, and Norseman. Pyrite in less concentrated form pervades the Australian geological scene. It is a persistent mineral below the oxidation zone. Pyrite, its presence, and its physical properties, are very relevant considerations in hard rock, soft rock, engineering, environmental, and hydrology geoscience investigations. It also has a very interesting history.Rickard (2015), in an outstanding book, comprehensively documents the general science of pyrite, its benefits, and its problems. For the mineralogist or mineral collector, Voynick Don Emerson (2011, 2018a, 2018b) and Jones (2016) provide good guides to systemsnsw@gmail.com pyrites occurrences and history. Lindgrens (1933) classic text still furnishes useful information on pyrite deposits. Deer, Howie, and Zussman (1992) summarise pyrites mineralogical features.Introduction This article reviews, quite subjectively, selectively, and Non omne quod fulget est aurum discursively, some of pyrites history, and presents experimental data to shed a little light on a somewhat ambiguous aspect of This medieval Latin caveat was used by William Shakespeare inpyrites physical propertiesits conductivity.1596 in the Merchant of Venice (Act 2, Scene 7): and by Miguel de Cervantes in 1615 in his Don Quixote (Part 2, Book 3). A summary of pyrites main properties is given in Table 1. Herein, pyrite refers to the cubic sulphide FeS 2 ; pyrites is used as the All that glisters is not gold umbrella term for a collection of yellowish metallic sulphides, So true. And, in nature, as geoscientists know, a lot of thesee Table 2. Note that marcasite is pyrites unstable low glittering is done by pyrite fools gold. But it is far from beingtemperature dimorph. Marcasite is a pyrites, it is not pyrite.a material worthless to humankind. Indeed, this sulphide itselfThree forms of pyrite are shown in Figure 1.often contains gold.Bright, brassy, brittle, ubiquitous pyrite is the most commonFiresulphide. Cryptocrystalline to coarsely crystalline, it crystallises over a wide temperature range and manifests many forms:Humankinds development was facilitated by agriculture, the cubes (with or without striations), prisms, octahedra,wheel etc. Predating all this was fire, without which progress pyritohedra (irregular dodecahedra with five sided faces), andwould have been impossible. This was appreciated by the rogue granular (no recognisable external isometric features, but theTitan demi-god Prometheus (careful foresight in ancient internal structure is cubic). Aggregates of crystals or grainsGreek) who is said to have fashioned man from clay and to have can form nodules, radiating suns, or bars (crystals stackedfurnished him with fire (pyr Gk.). The fire was in the form of in one direction). It manifests as disseminations, veins, orsparks inside a plant stem stolen from Olympia. This infuriated massive deposits in igneous, metamorphic and sedimentarythe boss-god Zeus, who punished Prometheus by chaining him settings. Its presence can be boon or bane. Pyrite may be ato a rock on Mt Caucasus where an eagle incessantly pecked guide to metallic mineralisation, or, owing to its included goldhis innards. So sad, such suffering, but at least, in this mythical content, may be economic mineralisation by itself. Pyrite mayversion, people had fire. Access to fire for early humans whether obscure indications of valuable mineralisation, or pose severeby Prometheus spark, a forest fire ignited by lightning, or a environmental problems in land use. Most geoscientists, inburning flare of natural gas venting from a fissure, was not the terrains they investigate, encounter and deal with pyritemuch use because such sources were not portable as hunter-sometime, or many times, in their careers. gatherers moved around.Pyrite occurs in many modes, from nanocrystalline dustPyrite, which sparks under percussion, provided portability in recent sediments to truly colossal lenses of solid pyrite,(until the Iron Age). Mastery of fire happened perhaps hundreds associated with quartz porphyries and Palaeozoic slates, in theof thousands or more years ago (the subject is controversial). It Rio Tinto deposits of Huelva Province west northwest of Seville,was the great instrument of change. Cooking plants and flesh Spain. Here pyrite has been open cut mined for millennia as arendered them safer and easier to digest, so a wider range of source of sulphur (by roasting), and for its included gold. Copperfoods became available. Smaller digestive systems and larger from the chalcopyrite also present. In the huge, low grade,brains evolved (Wrangham 2009). Fire extended the day. At auriferous, carbonate hosted Carlin style mineralisation, goldnight, fire kept big bities at bay. Around the hearth, or campsite, occurs along with mercury, arsenic and antimony as surfaceefforts to express opinions and relay information would DECEMBER 2019 PREVIEW 52'