Sinkankasite is a rare phosphate mineral occurring as delicate, thin bladed crystals or radial clusters. It is primarily found within complex granite pegmatites and is highly prized by mineral collectors due to its extreme scarcity and limited number of known localities.
Is this sinkankasite?
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 sinkankasite with a known reference. Sinkankasite sits at Mohs ~4, 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: vitreous to dull, vitreous on cleavages.
- 4Match the color rangeCompare against the expected color range: colorless, white.
- 5Look at form & habitCrystal system: triclinic. Typical habit: pseudomorphous.
Often confused with
Sinkankasite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Sinkankasite leaves white, Gormanite leaves pale green.
How to tell apart: Tinsleyite is the harder of the two (Mohs ~5 vs. ~4); streak differs, so Sinkankasite leaves white, Tinsleyite leaves pink.
Often found alongside sinkankasite
Minerals reported to co-occur with sinkankasite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- H₂MnAl(PO₄)₂(OH)·6H₂O
- Mohs hardness
- ~4
- Density
- 2.27 g/cm³
- Streak
- White
- Luster
- Vitreous to dull, vitreous on cleavages
- Transparency
- Transparent
- Crystal system
- Triclinic
- Crystal habit
- Pseudomorphous
- Cleavage
- On {100}, perfect; also a parting along {100} twin boundaries
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A late-stage hydrothermal alteration product of triphylite in complex zoned granite pegmatites
Where rockhounds find sinkankasite
Classic worldwide localities
- Barker (Ferguson) mine, five km southeast of Keystone, Pennington Co., South Dakota, USA
- Palermo #3 mine, near North Groton, Grafton Co., New Hampshire, USA
Field-hunting tip
Where it forms: A late-stage hydrothermal alteration product of triphylite in complex zoned granite pegmatites. If you start seeing vivianite, huréaulite, carbonate-apatite in float, you are in the right ground. Typical habit: pseudomorphous. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify sinkankasite?+
Where is sinkankasite found?+
What rocks look like sinkankasite?+
What minerals are found with sinkankasite?+
What kind of rock does sinkankasite form in?+
What is sinkankasite used for?+
Find sinkankasite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
