Schorlomite
Ca3(Ti,Fe3+)2(Si,Fe3+)3O12
A lustrous black titanium-rich garnet of the andradite series, found in alkaline igneous rocks like nepheline syenite and ijolite.
- Mohs hardness
- 7-7.5
- Color
- black to brownish black
- Type
- mineral
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Overview
Schorlomite is a rare, titanium-rich member of the garnet group, closely related to andradite and the black variety melanite. Its deep black color comes from substantial titanium (Ti4+) substituting into both the octahedral and tetrahedral sites of the garnet structure, along with ferric iron.
Like all garnets it is isometric (cubic) and forms hard, brittle crystals with a resinous to vitreous luster. It is prized by mineral collectors more than as a gem because of its opacity and dark color.
Schorlomite is part of a chemical continuum that includes morimotoite and kimzeyite, and many specimens labeled 'melanite' are actually titanium-bearing transitional material.
Formation & geology
Schorlomite crystallizes in silica-undersaturated alkaline igneous rocks, where excess alkalis and titanium favor exotic minerals. Typical hosts are nepheline syenites, ijolites, melilite-bearing rocks, and carbonatite complexes.
It forms at magmatic temperatures from melts enriched in calcium, titanium, and iron. It commonly occurs alongside other alkaline-rock minerals such as nepheline, aegirine, melanite garnet, perovskite, and titanite.
Notable localities include Magnet Cove, Arkansas (USA), the Kola Peninsula (Russia), Iron Hill (Colorado), and various East African and Italian alkaline volcanic centers.
How to identify it
Look for jet-black, hard isometric crystals (often dodecahedra or trapezohedra) with a resinous to submetallic luster set in an alkaline igneous matrix. Mohs hardness is about 7-7.5, and the streak is grayish to brownish.
It closely resembles melanite (black titanian andradite) and morimotoite, and the three are reliably distinguished only by chemical analysis. Distinguish it from black tourmaline (schorl) by garnet's lack of striations and its higher symmetry and crystal habit, and from magnetite by schorlomite's weak-to-absent magnetism and non-metallic streak.
Uses & significance
Schorlomite has no significant industrial or gem use because it is opaque and dark. Its main value is to mineral collectors and to petrologists, for whom it is a useful indicator of alkaline, silica-undersaturated magmatism.
Well-formed crystals from classic localities such as Magnet Cove are sought-after specimens. In metaphysical circles black garnets are loosely grouped with other dark stones said to offer grounding and protection, though there are no scientifically established properties.
Frequently asked questions
Is schorlomite the same as black tourmaline?
No. Black tourmaline is schorl, a borosilicate. Schorlomite is a titanium-rich garnet; the names are similar but the minerals are unrelated.
Why is schorlomite black?
Its color comes from abundant titanium and ferric iron in the garnet structure, the same chemistry that makes melanite garnet dark.
Is schorlomite a gemstone?
Not typically. It is opaque and dark, so it is collected as a mineral specimen rather than faceted as a gem.
Where is schorlomite found?
In alkaline igneous rocks such as nepheline syenites and carbonatites, with classic occurrences at Magnet Cove, Arkansas, and on Russia's Kola Peninsula.
Schorlomite guides
In-depth guides for identifying, valuing, and understanding Schorlomite.
