Friday Update – Smithsonite

CONTINUING along the theme of carbonates, we delve into the world of zinc carbonate. As with most carbonates, Smithsonite crystallizes within the trigonal crystal class, meaning that rhombic forms dominate.

Like Calcite before, pure Smithsonite is colourless, but traces of some base metals impart often striking colours, from blue and green from copper, yellow from cadmium and pink from cobalt or manganese. As a secondary species almost universally found in near surface oxidation zones, the mixing pot of chemistry is often much more diverse than that associated with the formation of Calcite, meaning that Smithsonite is often tinted in different shades of colour.

Most commonly, Smithsonite develops as banded botryoidal or stalactitic growths, but under rare conditions it crystallizes slowly into open spaces as larger rhombic crystal forms. Optimum conditions were evidently present within the extensive oxidation zones at Tsumeb and Berg Aukas mines in Namibia and it is from these two mines that most of the world’s finest specimens of Smithsonite crystals were found and again our selection today is strongly biased towards Tsumeb.

On the book front, if you are keen to learn more about this remarkable mineral species, we have available a couple of copies of the Extra Lapis volume on Smithsonite from 2010.

Next week we head to South America, and to Peru, a country steeped in mining heritage and of course wonderful mineral specimens. See you then.

Please note: Today's featured specimens are situated at both our US and UK showrooms.