Calcite, calcium carbonate, CaCO3 Although of little interest, this specimen is included in the collection, simply because it was collected in my very early collecting days. It was collected from a spoil heap at Tankerville mine, in the Shelve area of Shropshire, The calcite is just off white, and the cleavage planes can be clearly seen.
Gypsum is calcium sulphate dihydrate, CaSO4 . 2H2O This variety of rosette crystal habit is commonly referred to as a "desert rose". This is because it is found in arid desert conditions when shallow salt basins dry up. As the basin dries up the gypsum is forced to precipitate, and as it does so it incorprates grains of sand in its growth. This particular specimen is from Morocco, but similar specimens are found in most of the worlds deserts.
Millerite is nickel sulphide, NiS. The specimen is from waste heaps at Marine colliery, Ebbw vale, South Wales. Millerite is widespread throughout the south Wales coalfield, which was deposited during the late Carboniferous period. The specimen is quite small compared to others which have been found at this site, but it is the largest of the ones that I found. The acicular radiating needles are in a very small vhug of siderite. The photo is the best that I can manage with my meagre equipment, and will be replaced at a future date.
Okenite, CaSi2O. 5 . 2H2O is a colourless silicate mineral that is closely associated with zeolites. The cotton wool effect of this mineral is the result of very fine fibrous radiating crystals. This specimen is from the Poona district in India, probably from Malad quarry in Mumbai. Deccan lava flows in the late Cretaceous period which deposited massive areas of basalt, are the source of this mineral. Also visible on this specimen around the okenite are what are possibly small globular crystals of gyrolite.
Calcite is calcium Carbonate, CaCO3 and is widespread throughout Wales. Some of the best crystals are from limestone quarries in South Wales. This specimen, which was collected from Blaengwynlais quarry, near Cardiff, is a vhug of scalenahedral and rhombic crystals with step faces set in reddish limestone.