Esseneite is a rare pyroxene group mineral that typically occurs in pyrometamorphic rocks formed by the combustion of organic matter in bituminous sediments. It is most commonly found as microscopic or small grain-like inclusions within complex high-temperature contact metamorphic assemblages. Collectors prize it primarily as a curiosity due to its very restricted type localities and unique geochemical origin.
Is this esseneite?
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 esseneite with a known reference. Esseneite sits at Mohs 6, 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: reddish brown.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: anhedral to subhedral grains or small inclusions.
Often confused with
Esseneite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside esseneite
Minerals reported to co-occur with esseneite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- CaFe³⁺AlSiO₆
- Mohs hardness
- 6
- Density
- 3.54 g/cm³
- Colors
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent in thin crystals
- Crystal system
- Monoclinic
- Crystal habit
- Anhedral to subhedral grains or small inclusions
- Cleavage
- Perfect on {110}
- Rarity
- Rare
- Uses
- Collector, Scientific research
- Host rock
- A high-temperature, low-pressure, oxidized and quenched crystallization product derived from fused sediments contiguous to naturally combusted coal seams
Where rockhounds find esseneite
Classic worldwide localities
- Durham ranch, in the Powder River basin, 13 km northeast of Reno Junction and 25 km south of Gillette, Campbell Co., Wyoming, USA
Field-hunting tip
Where it forms: A high-temperature, low-pressure, oxidized and quenched crystallization product derived from fused sediments contiguous to naturally combusted coal seams. If you start seeing anorthite, melilite, magnetite-hercynite in float, you are in the right ground. Typical habit: anhedral to subhedral grains or small inclusions. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify esseneite?+
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What rocks look like esseneite?+
What minerals are found with esseneite?+
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Find esseneite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
