Jeffbenite is a rare magnesium aluminum silicate mineral discovered as a high-pressure phase in xenoliths from India. It typically occurs as small, clear, tabular crystals that closely resemble other silicate minerals like pyrope. It is of significant interest to researchers and high-end mineral collectors due to its unique structural relationship to the garnet group.
Is this jeffbenite?
5-step field checkRun through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.
- 1Test the hardnessTry to scratch jeffbenite with a known reference. Jeffbenite sits at Mohs ~7, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: white.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: deep emerald-green.
- 5Look at form & habitCrystal system: tetragonal. Typical habit: tabular crystals.
Often confused with
Jeffbenite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside jeffbenite
Minerals reported to co-occur with jeffbenite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Mg₃Al₂Si₃O₁₂
- Mohs hardness
- ~7
- Density
- 3.576 g/cm³
- Colors
- Deep emerald-green
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Tetragonal
- Crystal habit
- Tabular crystals
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Part of a composite inclusion with omphacitic pyroxene in an alluvial diamond; likely trapped in diamond in the deep upper mantle
Where rockhounds find jeffbenite
Classic worldwide localities
- São Luiz River, Juina district, Mato Grosso, Brazil
Field-hunting tip
Where it forms: Part of a composite inclusion with omphacitic pyroxene in an alluvial diamond; likely trapped in diamond in the deep upper mantle. If you start seeing ferropericlase, omphacitic pyroxene, olivine in float, you are in the right ground. Typical habit: tabular crystals. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify jeffbenite?+
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Find jeffbenite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
