Kosmochlor is a rare sodium-chromium pyroxene often found as an inclusion in iron meteorites or within deep-seated metamorphic rocks. It is highly valued by collectors for its intense, vivid emerald-green color, which is caused by its high chromium content. Identification in the field is difficult due to its visual similarity to jadeite and other pyroxenes, often requiring analytical confirmation.
Is this kosmochlor?
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 kosmochlor with a known reference. Kosmochlor 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: light green.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: emerald green.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: fibrous, massive, or as granular aggregates.
Often confused with
Kosmochlor vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Kosmochlor leaves light green, Jadeite leaves white; luster reads vitreous on Kosmochlor and subvitreous, pearly on cleavages on Jadeite.
How to tell apart: Streak differs, so Kosmochlor leaves light green, Diopside leaves white, gray, gray-green.
How to tell apart: Streak differs, so Kosmochlor leaves light green, Omphacite leaves greenish white.
Often found alongside kosmochlor
Minerals reported to co-occur with kosmochlor. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- NaCrSi₂O₆
- Mohs hardness
- ~6
- Density
- 3.51-3.60 g/cm³
- Colors
- Streak
- Light green
- Luster
- Vitreous
- Transparency
- Semitransparent
- Crystal system
- Monoclinic
- Crystal habit
- Fibrous, massive, or as granular aggregates
- Cleavage
- Good on {110}, (110) ^ (110) ~87°; parting on {001}
- Rarity
- Rare
- Uses
- Collector, Research
- Host rock
- A major constituent of some jadeitites; an accessory constituent of some iron meteorites
Where rockhounds find kosmochlor
Classic worldwide localities
- Williams Creek, Mendocino Co., California, USA
- Toluca, Coahuila, Hex River Mountains, and Canyon Diablo meteorites
- Tawmaw and other towns, Myitkyina-Mogaung district, Kachin State, Myanmar (Burma)
- Mocchie, Susa, Piedmont, Italy
Field-hunting tip
Where it forms: A major constituent of some jadeitites; an accessory constituent of some iron meteorites. If you start seeing chromian diopside, troilite, daubréelite in float, you are in the right ground. Typical habit: fibrous, massive, or as granular aggregates. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify kosmochlor?+
Where is kosmochlor found?+
What rocks look like kosmochlor?+
What minerals are found with kosmochlor?+
What kind of rock does kosmochlor form in?+
What is kosmochlor used for?+
Find kosmochlor on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
