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.
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