This rather small example of underground turmoil is the effect of Hydraulic brecciation, when shards of rock within a cavity implode into hot circulating silica rich fluid. Note the very angular shards of wall rock. There must have been some open cavities after the event, which allowed the cooling silica to grow in crystal form. This specimen came from Cafartha mine in the Central Wales orefield.
Bismuth is a chemical element, Bi. Although Bismuth is known as small occurrences in it's pure state, it is mostly extracted from two major ores of Bismuth, Bismuthinite ( 81% ) and Bismite ( 89% ). It has a rhombohedral lattice structure, and crystals grow with a "hopper" appearance .The stepped crystals form as a result of faster growth on the outer face compared to the inner face, possibly caused by an electrical charge on the outer surface. Hopper growth is also known in several other minerals, for instance, Halite, Galena, and others. I bought this synthetic specimen, lab grown, online, however the hopper appearance is not uncommon in natural deposits.
These agates were collected in the Coober Pedy area of Australia by the clubs co-founder Jim Nicholls. Coober Pedy is famous for the opals found there, but it seems that there is also a wide variety of agate. My favourite type of agate is the "crazy lace" variety which is one of the agates in the photograph.
Fuchsite, also referred to as chrome mica has the chemical formula KAl2(Si3Al)O10(OH)2 The colour can vary from pale green to deep emerald green, and is dependant on the amount of chromium. This specimen has quite a deep green colour, and has a silvery sheen in places. It was collected by our clubs co-founder, Jim Nicholls while living in Western Australia, possibly from a deposit at Cookes creek.
Woodwardite is a rare Hydrated Copper Sulfate found in weathered deposits at copper mines. The habit is usually described as botrioidal, as in malachite. These specimens however are simply encrustations. The specimens come from a type locality which is Castletown Bearhaven Copper Mines in County Cork, Ireland.