Sincosite is a rare vanadium phosphate mineral typically found as small, bright green, platy crystals. It is most often found in association with vanadium-bearing sedimentary rocks where it forms thin crusts or micaceous coatings on host rock surfaces.
Is this sincosite?
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 sincosite with a known reference. Sincosite sits at Mohs 1-2, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: green.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous, submetallic if partially dehydrated.
- 4Match the color rangeCompare against the expected color range: green, yellowish green, olive green, brownish green.
- 5Look at form & habitCrystal system: tetragonal. Typical habit: aggregates, platy, scaly.
Often confused with
Sincosite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Sincosite leaves green, Roscoelite leaves greenish white; luster reads vitreous, submetallic if partially dehydrated on Sincosite and pearly on Roscoelite.
How to tell apart: Streak differs, so Sincosite leaves green, Tyuyamunite leaves light yellow; luster reads vitreous, submetallic if partially dehydrated on Sincosite and adamantine, pearly on {001}, may be dull to waxy if massive on Tyuyamunite.
Often found alongside sincosite
Minerals reported to co-occur with sincosite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ca(VO)₂(PO₄)₂·4H₂O
- Mohs hardness
- 1-2
- Density
- 2.97 g/cm³
- Streak
- Green
- Luster
- Vitreous, submetallic if partially dehydrated
- Transparency
- Translucent to transparent in small grains
- Crystal system
- Tetragonal
- Crystal habit
- Aggregates, platy, scaly
- Cleavage
- Perfect on {001}; good on {110}; poor on {010}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In veinlets in black carbonaceous shale (Sincos, Peru)
Where rockhounds find sincosite
Classic worldwide localities
- Ross Hannibal mine, about four km southwest of Lead, Lawrence Co., South Dakota, USA
- Bloomington, Bear Lake Co., and in the Enoch Valley phosphate mine, Soda Springs, Caribou Co., Idaho, USA
- Wilson Springs (Potash Sulphur Springs) mine, Garland Co., Arkansas, USA
- Gold Quarry mine, near Carlin, Maggie Creek district, Eureka Co., Nevada, USA
- Sincos, Junin Province, Peru
Field-hunting tip
Where it forms: In veinlets in black carbonaceous shale (Sincos, Peru). If you start seeing gypsum, minyulite in float, you are in the right ground. Typical habit: aggregates, platy, scaly. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify sincosite?+
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Find sincosite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
