Pool Spar

Pool spar are simply well-defined crystals that grow underwater in cave pools, and are a subtype of spar crystal. Usually, they are composed of calcite. Often the pool in which the crystals grew has evaporated or fills only seasonally. A water line is usually clearly visible as in photos 3-9. Pool spar is often found on the bottom of shelfstone. Pool spar may also coat the end of a stalactite that extends into a pool that has inundated it, in which case it is called a bottlebrush, which has a separate page here.

Most pool spar is of the “dogtooth” variety, coming to a point as shown the first two photos. But other pool spar, especially that formed along the flat surface of the pool, may form in a triangular shape, as in photo #4, or lily pads as in photo #3.