About
Magnesium Spinel, often just known plainly as Spinel, is the most common and well-known member of the Spinel series. Gahnite is also known among collectors, while the other two members (Hercynite and Galaxite) are very rare and seldom represented in collections.
For additional information, see the gemstone section on Spinel.
Crystal Forms & Aggregates
Other ID Marks
Complex Tests
Striking Features
Environment
Varieties
✓ common · ✗ uncommon
- Gahnite— Zinc-rich end-member of the Spinel mineral series. Gahnite is scientifically recognized as an individual mineral species.
- Gahnospinel— Mixture of Magnesium Spinel and Gahnite, with a chemical formula of (Mg,Zn)Al2O4.
- Galaxite— Manganese-rich end-member of the Spinel mineral series. Galaxite is scientifically recognized as an individual mineral species.
- Hercynite— Iron-rich end-member of the Spinel mineral series. Hercynite is scientifically recognized as an individual mineral species.
- Pleonast— Opaque, dark blue or green to black variety of Spinel.
- Rubicelle— Yellow to orange variety of Spinel.
- Ruby Spinel— Transparent red gem variety of Spinel.
- Almandine Spinel— Spinel with a violet color.
- Balas Ruby— Gem Spinel with a pink to pale red color.
- Ceylonite— Magnesium Spinel containing traces of iron, which gives it a dark green to black color.
- Chlorospinel— Grass green variety Magnesium Spinel with the color caused by traces of iron and copper.
- Chrome-spinel— Chrome-rich variety of Spinel; synonym of Picotite.
- Chromohercynite— Chromium rich variety of Hercynite.
- Chrysomelane— Synonym of Hercynite.
- Picotite— Chromium and magnesium-rich variety of Hercynite; may also describe brown Spinel.
Uses
Noteworthy Localities
Madagascar also has several notable localities in Tulear Province, especially at Ambatomainty, where large clusters of black crystals have occurred. Tanzania also has noted occurrences in Ipanko and Morogoro. A European location of note is the Fassa Valley (Val D'Fassa), Trento Province, Italy. Spinel has been found in Canada, in Ross Township, Renfrew Co., Ontario; and in the Parker mine, Notre-Dame-du-Laus, Quebec.
In the U.S., the finest crystals came from the Franklin Marble region which stretches from Sussex Co., New Jersey to Orange Co., New York. Classic Spinel localities in that region in New Jersey include the Limecrest Quarry, Sparta; the Sterling Hill Mine, Ogdensburg; and Franklin, Sussex Co. In New York, they include Amity, Edenville, and Warwick, Orange Co. Amity is perhaps the finest U.S. occurrence, where enormous black octahedrons were found in the 18th century. Enormous Spinel crystals were also found in a lost locality in Monroe, Orange Co., New York. Spinel was also found at Bolton, Worcester Co., Massachusetts, and opaque blue crystal clusters occur near Helena, Lewis and Clark Co., Montana.
In the U.S., Gahnite has come from Franklin and Ogdensburg, Sussex Co., New Jersey; the Mt. Apatite District, Auburn, Androscoggin Co., Maine; and the Davis Mine, Rowe, Franklin Co., Massachusetts.
Common Mineral Associations
Distinguishing Similar Minerals
Magnetite - Softer (5½ - 6½), strongly attracted to magnets.
Franklinite - Softer (5½ - 6½), slightly attracted to magnets.
Zircon - Different crystal forms.
Chromite - Softer (5½), heavier (4.1 - 5.0).
Garnet - Different crystal forms.
Photos
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