Dolomite

Dolomite from Teutonic Bore Mine, Ten Mile Outcrop, Leonora, Western Australia, Australia, measuring 68 × 48 × 32 mm and weighing 116 grams. The detailed locality is a particularly useful part of this specimen's record. It gives a familiar carbonate mineral a specific Western Australian setting and allows the piece to be compared with other material from the same occurrence.

Dolomite is a calcium-magnesium carbonate, distinct from Calcite even though the two minerals are frequently discussed together. Its ordered arrangement of calcium and magnesium is part of what gives it a separate mineral identity. A collection of carbonates becomes more informative when those differences are recognised, rather than grouping all similar-looking material under one familiar name.

Whitish crystal patches sit against dark reddish-brown matrix, giving the specimen a clear light-and-dark contrast. Its roughly triangular outline provides a natural overall shape, while the smaller pale groups add detail within it. The piece lends itself to a display that keeps some matrix visible, so that the distribution of the carbonate remains part of the story. The provenance records the David Vince and Ruth Coulsell collections. Those names give the piece a collecting history to accompany its precise source. It is a useful specimen for someone who enjoys the quieter side of mineral collecting, where a common mineral gains individuality through its locality, dimensions and documented passage through earlier collections.