Calcite – Eskifjordur, Iceland. This remote area of Iceland is the type locality for the Iceland Spar variety of calcite (CaCO3; type locality is the place where a mineral or rock best exemplifies its standard description, often where it was first discovered). Iceland Spar calcite is exceptionally clear and optically transparent, whereas other types of calcite can have a wide range of colors and translucencies (see photo in the Problem 10 placemark). Given this, which of the following is not a diagnostic property for calcite?
a. cleavage at three directions not at ~90°.
b. hardness of 3.
c. color.
d. effervesces (forms CO2 bubbles) with hydrochloric acid.

Calcite is a carbonate mineral which is found in different countries and has over 800 different forms. Calcite has cleavage at three directions which forms rhombic shape but the angles is not 90 degrees. It has hardness of 2 and is effervesces with hydrochloric acid. Color is not a diagnostic property of Calcite.

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