spinel

or spi·nelle

[ spi-nel, spin-l ]

Phonetic (Standard)IPA

noun

any of a group of minerals composed principally of oxides of magnesium, aluminum, iron, manganese, chromium, etc., characterized by their hardness and octahedral crystals.
a mineral of this group, essentially magnesium aluminate, MgAl 2 O 4 , some varieties being used as gems.

spinel

/ spɪˈnɛl /

any of a group of hard glassy minerals of variable colour consisting of oxides of aluminium, magnesium, chromium, iron, zinc, or manganese and occurring in the form of octahedral crystals: used as gemstones
a hard, glassy mineral composed of magnesium-aluminium oxide found in metamorphosed limestones and many basic and ultrabasic igneous rocks. Formula: MgAl 2 O 4

spinel

/ spĭ-nĕl′ /

A hard, variously colored cubic mineral, having usually octahedral crystals and occurring in igneous and metamorphosed carbonate rocks. The red variety is valued as a gem and is sometimes confused with the ruby. Chemical formula: MgAl 2 O 4 .
Any of a group of minerals that are oxides of magnesium, iron, zinc, manganese, or aluminum.

Origin of spinel¹

1520–30; < French spinelle < Italian spinella, equivalent to spin ( a ) thorn (< Latin spīna ) + -ella -elle

Origin of spinel¹

C16: from French spinelle, from Italian spinella, diminutive of spina a thorn, from Latin; so called from the shape of the crystals

The rock—which also contains the plain-old mineral plagioclase—includes pink spinel, a prized jewel on Earth.

The rubies of Burma are found in crystalline limestones and are constantly accompanied by precious spinel (or balas-ruby).

Some of the alumina and iron oxide may occasionally be chemically combined, so as to form an iron spinel, or hercynite.

Then follows the topaz, which, with spinel and chrysoberyl, has a hardness of 8; whilst quartz falls a degree lower.

Mention has been made above of a stone frequently substituted for the true ruby, called the “spinel” or “balas” ruby.

The spinel and ruby occur together in nature, stones from Burma being as often spinel as true Oriental ruby.

April 23, 2024inveterate

[in-vet-er-it ]

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