Edgrewite is an extremely rare calcium silicate member of the humite group found in skarn zones. It typically occurs as small, indistinct grains within limestone contact metamorphic environments, often requiring X-ray diffraction for definitive identification.
Is this edgrewite?
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 edgrewite with a known reference. Edgrewite 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. Edgrewite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Edgrewite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: colorless, white, gray.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: granular, anhedral crystals.
Often confused with
Edgrewite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside edgrewite
Minerals reported to co-occur with edgrewite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ca₉Si₄O₁₆F₂
- Mohs hardness
- 6
- Density
- 3.17 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Monoclinic
- Crystal habit
- Granular, Anhedral Crystals
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Skarn Deposits Formed By Contact Metamorphism
- Typical price
- Not publicly traded; mostly of research interest.
Where rockhounds find edgrewite
Classic worldwide localities
- Kizil-Kaya, Alai Range, Kyrgyzstan
- Aktyuz ore field, Kyrgyzstan
Field-hunting tip
Look in skarn deposits formed by contact metamorphism country — that is the host setting where edgrewite typically forms. If you start seeing calcite, wollastonite, diopside in float, you are in the right ground. Field specimens usually show a granular, anhedral crystals habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find edgrewite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
