There simply is no end to the varieties of calcite. There are several varieties of calcite and it would be impossible to describe them all. However there are a few standouts. This variety appears as a double pyramid or dipyramid , but is actually a distinctly different form. The point of the scalenohedron is sharp and resembles the canine tooth of a dog, hence the name.
Calcite is the primary mineral component in cave formations.
It is the fact that calcite is readily dissolved that these formations occur. Overlying limestones or marbles are dissolved away by years and years of slightly acidic ground water to percolate into the caverns below. In fact the caverns themselves may have been the result of water dissolving away the calcite rich rock. As the calcite enriched water enters a relatively dry cavern, the water starts to evaporate and thus precipitate the calcite. The resulting accumulations of calcite are generally extremely pure and are colored if at all, by very small amounts of iron or other impurities.