Reddish mineral

• Occurs in various colors that are used as gemstones
• Ruby variety
• Rubylike gemstone
• Ruby ___ (gem)
• Gemstone often passed off as a ruby
• Gemstone mined in Sri Lanka
• Rubylike gem

The Collaborative International Dictionary Word definitions in The Collaborative International Dictionary
Spinel \Spi*nel"\, Spinelle \Spi*nelle"\, n. [F. spinelle, or LL. spinellus, perhaps from L. spina a thorn, a prickle, in allusion to its pointed crystals.] (Min.) A mineral occuring in octahedrons of great hardness and various colors, as red, green, blue, ...

Wikipedia Word definitions in Wikipedia
Spinel is the magnesium aluminium member of the larger spinel group of minerals. It has the formula MgAlO in the cubic crystal system . Its name comes from Latin "spina" (arrow). Balas ruby is an old name for a rose-tinted variety.