calcite - cleaved rhombs of translucent calcite - teaching hand specimen
Calcite: CaCO3 - cleavage romb pair
Calcite is an extremely common rock forming mineral. In pegmatites it forms large masses and it makes up some limestones almost entirely. It has a large variety of crystal forms, but these do not include the rhombus-shaped pieces that are sold as “calcite crystals.” The rhombs produced by cleaving calcite in three directions between rows of atoms.
When calcite is free of impurities and is optically clear, it exhibits double refraction. When optical calcite is placed above a line drawn on paper and rotated, the drawn line doubles and becomes single depending on the angle of rotation. This calcite is not clear enough to demonstrate this.
The white calcite is from China. It is sold as two rhombs in a set. The golden is from Morocco. We have no accurate locality information other than the country of origin. These are perfect cleavage rhombs and clearly show the three directions of cleavage.
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