The derivation of the name "spinel" is uncertain. It may mean "spark" (Greek) or "point" (Latin)/ It occurs in all colors, the most popular being ruby-like red. It's coloring comes from chrome and iron. Large stones, as well as star spinels are very rare. The blue variety is sensitive to high temperatures. The dark green to black opaque spinels is called Ceylonite, also pleonaste (Greek - surfeit, because of its numerous crystal faces). The brown variety is called Piconite (French), yellow is called Rubicelle (diminutive French word for ruby) and the pale red is known as balas ruby (after a region in Afghanistan).