Friday, September 19, 2014
The stamp on this Liechtenstein stamp of 1989 depicts a Calcite crystal. The stamp is one of a set of three on the subject of crystals.
Calcite is a carbonate mineral and the most stable polymorph of calcium carbonate (CaCo3 ).
The other polymorphs are the minerals aragonite and vaterite. Aragonite will change to calcite at 380–470°C, and vaterite is even less stable.
High-grade optical calcite was used in World War II for gun sights, specifically in bomb sights and anti-aircraft weaponry. Also, experiments have been conducted to use calcite for a cloak of invisibility. Microbiologically precipitated calcite has a wide range of applications, such as soil remediation, soil stabilization and concrete repair.
Thank you Merja.