Majorite Identification Guide

What Majorite Looks Like

Majorite is a rare, high-pressure garnet-group mineral — a magnesium-rich silicate, Mg3(MgSi)(SiO4)3 — that forms only at the extreme pressures of the deep mantle (transition zone). It is found in shocked meteorites and as inclusions in deep-derived diamonds, so most people will only encounter it in research collections, not the field.

• Color: typically purple, violet, to colorless, sometimes greenish (depending on chemistry)
• Luster: vitreous
• Transparency: transparent to translucent in tiny grains
• Habit: isometric garnet structure, usually as micro-grains, shock veins, or diamond inclusions rather than visible crystals

Step-by-Step Field ID Checklist

Majorite essentially cannot be hand-identified in the field — confirmation requires lab instruments. Practical context clues:

1. Setting: look for it in shock-melt veins of meteorites or as inclusions in mantle diamonds.
2. Garnet structure: confirmed by X-ray/Raman as cubic garnet despite unusual silicon coordination.
3. Association: found with other high-pressure phases (ringwoodite, wadsleyite, akimotoite) in shocked chondrites.
4. Grain size: typically microscopic, requiring a microprobe to identify.

Key Diagnostic Tests

• Mohs hardness: ~7-7.5 (garnet range).
• Cleavage: none (garnet group).
• Optics: isotropic.
• Specific gravity: high, ~3.5-3.6+.
• Definitive ID: electron microprobe, Raman spectroscopy, and X-ray diffraction — needed because of its high silicon content and tiny size.

Common Look-Alikes and How to Tell Them Apart

• Ordinary garnet (pyrope/almandine): chemically and structurally similar, but majorite has excess silicon in octahedral sites — only chemical analysis distinguishes it.
• Other meteorite high-pressure phases (ringwoodite, akimotoite): require spectroscopic/structural analysis to tell apart.
• Pyroxene: majorite forms a solid solution with pyroxene compositions; lab work resolves it.

Where It Is Typically Found

Majorite occurs in shock-metamorphosed (shocked) meteorites — its type material is from the Coorara chondrite, Australia — and as inclusions in deep-mantle (sublithospheric) diamonds. It also forms experimentally at transition-zone pressures.