Diamond (from the ancient Greek adámas "unbreakable") is a metastable allotrope of carbon. Diamond is renowned as a mineral with superlative physical qualities. In particular, diamond has the highest hardness and thermal conductivity of any bulk material. Diamond also has high optical dispersion (ability to disperse light of different colours). Diamonds are formed at high temperature and pressure deep in the Earth's mantle. Diamonds are brought close to the Earth′s surface through volcanic eruptions by a magma, which cools into igneous rocks known as kimberlites and lamproites.
Diamond is the hardest known natural material on the Mohs scale of mineral hardness, where mineral hardness is defined as resistance to scratching and is graded between Talc 1 (softest) and Diamond 10 (hardest). Diamond's hardness has been known since antiquity, and is the source of its name. The hardness of diamond contributes to its suitability as a gemstone. Because it can only be scratched by other diamonds, a diamond maintains its polish extremely well. Diamond is well-suited to daily wear because of its resistance to scratching, perhaps contributing to its popularity as the preferred gem in engagement rings.
Diamonds were discovered at Echunga in the Mt Lofty Ranges during the late 1800s, despite several extensive exploration programs the primary source of the stones still remains unknown to this day. Mystery surrounds the origin of these diamonds as no Kimberlite pipe has ever been uncovered in this area. Approximately 50 saleable diamonds were found in the Echunga Goldfields between 1859 and 1886. The largest being the "Glover Stone" at 5.25ct, named after its discoverer, John Glover in 1877. One of the diamonds was found after a dream. "Rennals dreamt that he saw an angel pointing to the spot at the foot of Poor Man's Hill and heard a voice telling him to dig. His mate, not believing him, threatened to throw Rennals into the dam if he did not continue with their usual gold prospecting. A struggle took place near the edge of the water, but the ground gave way and his mate fell in, putting an end to his objections. Rennals continued searching and soon found his diamond." The Advertiser 16 June 1909.
Diamonds are the hardest minerals. Mt Lofty is the highest peak in the ranges and therefore must be the hardest local mineral. Coincidence? You must wonder. To be sure you will need to see if you can scratch the exposed rock of Mt Lofty with a diamond. Where will you get a diamond? I gave my love a beautiful gem for our engagement. But does Squeaky dare borrow the stone? In any case see if you can find a diamond in the minerals of Mt Lofty. What is the grain size of the local stone? Estimate the Moh's hardness? Email these two answers to Sneaky Squeaky for your prize.