Collinsite is a rare hydrated calcium magnesium phosphate typically found as radiating fibrous or spherulitic aggregates. It is often discovered within phosphate nodules or secondary cavities and is highly prized by collectors for its distinctive radial crystal habit.
Is this collinsite?
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 collinsite with a known reference. Collinsite sits at Mohs 3.5-5, 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: subvitreous, silky if fibrous.
- 4Match the color rangeCompare against the expected color range: colorless, white, light brown.
- 5Look at form & habitCrystal system: triclinic. Typical habit: radiating fibrous masses, globular, spherulitic.
Often confused with
Collinsite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Luster reads subvitreous, silky if fibrous on Collinsite and pearly to subadamantine, vitreous on the {001} cleavage on Fairfieldite.
How to tell apart: Collinsite is noticeably harder (Mohs 3.5-5 vs. 2.5); streak differs, so Collinsite leaves white, Mitridatite leaves olive-green; luster reads subvitreous, silky if fibrous on Collinsite and dull, earthy to resinous on Mitridatite.
Often found alongside collinsite
Minerals reported to co-occur with collinsite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ca₂Mg(PO₄)₂·2H₂O
- Mohs hardness
- 3.5-5
- Density
- 2.93-2.95 g/cm³
- Streak
- White
- Luster
- Subvitreous, silky if fibrous
- Transparency
- Translucent
- Crystal system
- Triclinic
- Crystal habit
- Radiating fibrous masses, globular, spherulitic
- Cleavage
- Fair on {001} and {010}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A secondary weathering product typically incrusting other minerals
Where rockhounds find collinsite
Classic worldwide localities
- Tip Top mine, 8.5 km southwest of Custer, Custer Co., South Dakota, USA
- Foote mine, near Kings Mountain, Cleveland Co., North Carolina, USA
- François Lake, south of Babine Lake, Coast district, British Columbia, and as Big Fish River–Rapid Creek area, Yukon Territory, Canada
- Milgun Station, Western Australia, and a zincian variety from Reaphook Hill, near Blinman, Flinders Ranges, South Australia
- Kovdor massif, Kola Peninsula, Russia
Field-hunting tip
Where it forms: A secondary weathering product typically incrusting other minerals. If you start seeing carbonatian fluorapatite, bitumen, parahopeite in float, you are in the right ground. Typical habit: radiating fibrous masses, globular, spherulitic. Train your eye for that shape before scanning the outcrop.
Common questions
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Find collinsite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
