• Agate
• Alexandrite
• Amber
• Amethyst
• Anyolite
• Aquamarine
• Aventurine
• Beryl
• Carnelian
• Chalcedony
• Chrysoberyl
• Citrine
• Coral
• Corundum
• Diamond
• Emerald
• Garnet
• Hematite
• Ivory
• Jade
• Jasper
• Jet
• Lapis Lazuli
• Malachite
• Mother of Pearl
• Obsidian
• Olivine
• Onyx
• Opal
• Pearl
• Peridot
• Quartz
• Rosalite
• Rose Quartz
• Ruby
• Sapphire
• Spinel
• Tanzanite
• Thulite
• Tiger's-eye
• Topaz
• Turquoise
• Tourmaline
• Zircon
• Zoisite

Cleavage

In mineralogy, the tendency of crystalline materials to split along definite planes, creating smooth surfaces, of which there are several named types:

• Basal cleavage: cleavage parallel to the base of a crystal, or to the plane of the lateral axes.
• Cubic cleavage: cleavage parallel to the faces of a cube.
• Diagonal cleavage: cleavage parallel to a diagonal plane.
• Lateral cleavage: cleavage parallel to the lateral planes.
• Octahedral, Dodecahedral, or Rhombohedral cleavage: cleavage parallel to the faces of an octahedron, dodecahedron, or rhombohedron.
• Prismatic cleavage, cleavage parallel to a vertical Prism.