Adelite is a relatively rare calcium magnesium arsenate mineral typically found in metamorphosed manganese deposits. It most commonly occurs in botryoidal, crusty, or massive habits, occasionally showing distinct yellowish-green to gray-green coloration and a characteristic yellow fluorescence under short-wave UV light.
Is this adelite?
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 adelite with a known reference. Adelite sits at Mohs 5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Adelite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Adelite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: green, grayish-green, yellowish-green, white.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: crusts, botryoidal, massive, sometimes as small prismatic crystals.
Often confused with
Adelite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside adelite
Minerals reported to co-occur with adelite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- CaMgAsO₄OH
- Mohs hardness
- 5
- Density
- 3.73 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Orthorhombic
- Crystal habit
- Crusts, Botryoidal, Massive, Sometimes as Small Prismatic Crystals
- Cleavage
- None
- Fluorescence
- Yellow Under SW UV
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Metamorphosed Manganese Ore Deposits
- Typical price
- $20-150 for thumbnail to small cabinet specimens
Where rockhounds find adelite
Classic worldwide localities
- Langban, Sweden
- Nordmark, Sweden
- Franklin, New Jersey, USA
- Sterling Hill, New Jersey, USA
Field-hunting tip
Look in metamorphosed manganese ore deposits country, the host setting where adelite typically forms. If you start seeing calcite, dolomite, hausmannite in float, you are in the right ground. Field specimens usually show a crusts, botryoidal, massive, sometimes as small prismatic crystals habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find adelite on the map
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