TWO BASIC SHAPES:
While this shape is the most widely used in the market, flat crystals are susceptible to shattering or cracking. If used underwater, the flat shape might become reflective when seen at certain angles or if no coating is applied on the crystal.
A domed shape distributes any force applied to it evenly around the crystal and is therefore more resistant to shattering and cracking. However, the higher the curvature, the higher the risk of damage and abrasion.