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.