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, brown, and black, the
red variety being the gem spinel ruby. It consist essentially
of alumina and magnesia, but commonly contains iron and
sometimes also chromium.
Note: The spinel group includes spinel proper, also
magnetite, chromite, franklinite, gahnite, etc., all of
which may be regarded as composed of a sesquioxide and
a protoxide in equal proportions.
Source: Webster's Revised Unabridged Dictionary (1913)
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