Is a spinel a ruby?

Faceted spinel: Several pretty facet-cut spinels. It is easy to see how spinel can be confused with ruby and sapphire or used as an alternative stone. These spinels are about 4 1/2 millimeters in size and weigh a little less than 1/2 carat each. The top three red and pink stones were cut from material mined in Myanmar. read more

Spinel ( / s p ɪ ˈ n ɛ l /) is the magnesium aluminium member of the larger spinel group of minerals. It has the formula MgAl 2 O 4 in the cubic crystal system. Its name comes from Latin "spina" (arrow). Balas ruby is an old name for a rose-tinted variety of spinel. read more

The deep-red variety, often called Ruby Spinel, is the most prized form, and is a very good substitute for Ruby. Spinel is also an important pink gemstone. The opaque, black variety, known as Pleonast, has a good luster and is used as a black gemstone. Spinel naturally occurs in octahedral crystals. read more