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. Streak: white.
- 3Read the lusterHold the specimen under a strong light. Luster: resinous.
- 4Match the color rangeCompare against the expected color range: green, blue gray, gray, yellow, light green.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: massive.
Often confused with
Adelite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Luster reads resinous on Adelite and subadamantine to silky in aggregates on Austinite.
How to tell apart: Streak differs, so Adelite leaves white, Conichalcite leaves green; luster reads resinous on Adelite and vitreous to somewhat greasy on Conichalcite.
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
- 3.71-3.76 g/cm³
- Streak
- White
- Luster
- Resinous
- Transparency
- Translucent to transparent
- Crystal system
- Orthorhombic
- Crystal habit
- Massive
- Cleavage
- Indistinct
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A rare mineral in a metamorphosed Fe–Mn orebody (Långban, Sweden); on willemite-franklinite ore from a metamorphosed stratiform zinc orebody (Franklin, New Jersey, USA)
Where rockhounds find adelite
Classic worldwide localities
- Sterling Hill, Ogdensburg, and Franklin, Sussex Co., New Jersey, USA
- Långban and at Jakobsberg, Värmland, and in the Kittel mine, Nordmark, Sweden
- St. Andreasberg, Harz Mountains, Germany
Field-hunting tip
Where it forms: A rare mineral in a metamorphosed Fe–Mn orebody (Långban, Sweden); on willemite-franklinite ore from a metamorphosed stratiform zinc orebody (Franklin, New Jersey, USA). If you start seeing sarkinite, arsenoclasite, braunite in float, you are in the right ground. Typical habit: massive. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify adelite?+
Where is adelite found?+
Is adelite safe to handle?+
What rocks look like adelite?+
What minerals are found with adelite?+
What kind of rock does adelite form in?+
What is adelite used for?+
Find adelite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
