Aragonite.

Aragonite.

Aragonite, Calcium carbonate, CaCO3  has the same chemical composition as calcite, and vaterite. These three minerals are polymorphs of calcium carbonate, each with a different crystal lattice, so each one with a different crystal habit. Aragonite crystals are often pseudohexagonal and prismatic, as are the twinned crystals in this specimen from Morocco. Aragonite is not a stable polymorph, and will eventually  alter to calcite.

Calcite.

Calcite.

Calcite, Calcium carbonate,  CaCO3 This specimen is one of many collected from Taffs Well quarry, Cardiff , South Wales. There are several varieties of crystal to be found at this quarry. In this specimen the crystals are stubby and prismatic, with a pale cream colouration. The crystals have quite obvious horizontal striations, and are growing from a base of massive calcite.

Labradorite.

Labradorite.

Labradorite, ((Ca,Na)(Al,Si)4O8   is a feldspar mineral and is an intermediate to calcic member of the plagioclase feldspar series. When polished it's iridescent properties are revealed in an effect known as labradorescence. For this reason, it is often used to make jewelery. This specimen displays the plagioclase content, which is usually 40" to 60%. and comes from Larvic in Norway.

Inesite

Inesite

Inesite, is a complex inosilicate mineral, with a formula Ca2Mn7Si10O28(OH)2 . 5 To give it a full title, it is a hydrous calcium manganese silicate. The appearance of the specimen is true to type with prismatic pink coloured crystals, with chisel shaped terminations. The specimen is from Kuruman in South Africa.  

Calcite

Calcite

Calcite, Calcium carbonate, CaCO3  This simple specimen is part of a larger druse of scalenahdral crystals on a limestone base. The crystals are well formed and have a colour which could be called light cream. The origin is Colemans limestone quarry, Mendip hills, Somerset.