Aragonite, CaCO3 is a high pressure polymorph of Calcium carbonate. It is metastable near the earths surface, and will eventually decompose to the form of calcite. The specimen which is from the boulder clay at Speeton in Yorkshire has three distinct components, first a limestone base, then a deposit of very fine aragonite crystals, and finally a second generation deposit of closely packed dog tooth aragonite crystals.
Actinolite is a highly complex silicate, asbestos mineral with a formula too complicated for this short note. The specimen is from the contact zone between carbonate rock and a hydrothermal quartz body, at Selasvatn in the region of vegarshei, Aust-Agder, in Norway. In the specimen, dark green Actinolite is in the asbestiform habit of long, thin fibrous crystals. A higher presence of iron correlates with a deeper green colour.
Sphalerite, (Zn,Fe)S, Zinc sulphide, is the main ore of zinc, and is usually associated with galena. The specimens here were collected from Driggeth mine, Caldbeck, Cumbria. The small, brilliant black crystals of sphalerite are embedded in cavities in the limestone rock. The local geology suggests that the rocks here are Ordovician in age.
Gypsum, CaSO4 . 2H2O calcium sulphate dihydrate, is an evaporite mineral. This specimen was formed as a saline residue arising from the evaporation of an enclosed basin of sea water. Of the two specimens, one appears to be a loose aggregate, and the smaller one has obvious layering. The location is loosely given as Crete.
Analcime, Na(AlSi2O6) . H20 is a tectosilicate and classed as a zeolite. The specimen is from Croft quarry in Leicestershire, which is a noted site for analcime. The quarry is in igneous tonalite rocks of Ordovician age. The few crystals on the base of the specimen are trapezohedral in form.