Omphacite is a sodic-calcic pyroxene that serves as a defining mineral of eclogite, a high-pressure metamorphic rock. Collectors typically look for it as dark green, dense massive grains or subhedral crystals embedded in garnet-rich eclogite matrices.
Is this omphacite?
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 omphacite with a known reference. Omphacite sits at Mohs 5-6, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: greenish white.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous to silky.
- 4Match the color rangeCompare against the expected color range: grass green, dark green.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: anhedral grains, massive.
Often confused with
Omphacite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Omphacite leaves greenish white, Diopside leaves white, gray, gray-green.
How to tell apart: Streak differs, so Omphacite leaves greenish white, Jadeite leaves white; luster reads vitreous to silky on Omphacite and subvitreous, pearly on cleavages on Jadeite.
How to tell apart: Streak differs, so Omphacite leaves greenish white, Aegirine leaves pale yellowish gray.
Often found alongside omphacite
Minerals reported to co-occur with omphacite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (Ca,Na)(Mg,Fe²⁺,Al,Fe³⁺)Si₂O₆
- Mohs hardness
- 5-6
- Density
- 3.16-3.43 g/cm³
- Colors
- Streak
- Greenish white
- Luster
- Vitreous to silky
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Anhedral grains, massive
- Cleavage
- Good on {110}, (110) ^ (110) ~87°; parting on {100}
- Rarity
- Uncommon
- Uses
- Collector, Geological indicator
- Host rock
- A major constituent of eclogite, commonly in kimberlite pipes; from some ophiolites and glaucophane-bearing blueschist facies rocks
Where rockhounds find omphacite
Classic worldwide localities
- Tiburon Peninsula, Marin Co., and on into Sonoma Co., California, USA
- Hof, near Bayreuth, Bavaria, Germany
- Kupplerbrunn, Saualpe, and Gertrusk, Carinthia, Austria
- Eiksundsal, Sunmøre, Naustdal, Vanelvsdalen, and Möre, Norway
- Yakutia diamond pipes, as at Mir, Zagadochnaya, and Obnazhennya, Russia
- Kimberley, Cape Province, South Africa
Field-hunting tip
Where it forms: A major constituent of eclogite, commonly in kimberlite pipes; from some ophiolites and glaucophane-bearing blueschist facies rocks. If you start seeing garnet, quartz, kyanite in float, you are in the right ground. Typical habit: anhedral grains, massive. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify omphacite?+
Where is omphacite found?+
What rocks look like omphacite?+
What minerals are found with omphacite?+
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What is omphacite used for?+
Find omphacite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
