Joosteite is a rare phosphate mineral typically found as an alteration product within granite pegmatites. It usually occurs in massive or granular habits associated with other triphylite group members in the Jooste pegmatite of Namibia.
Is this joosteite?
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 joosteite with a known reference. Joosteite 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. Joosteite leaves a brownish black streak.
- 3Read the lusterHold the specimen under a strong light. Joosteite typically shows a sub-metallic luster.
- 4Match the color rangeCompare against the expected color range: black, brown.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: massive, granular.
Often confused with
Joosteite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Streak differs — Joosteite leaves brownish black, Triphylite leaves white; luster reads sub-metallic on Joosteite and vitreous on Triphylite.
How to tell apart: Streak differs — Joosteite leaves brownish black, Heterosite leaves light violet to brownish-purple; luster reads sub-metallic on Joosteite and dull to sub-metallic on Heterosite.
Often found alongside joosteite
Minerals reported to co-occur with joosteite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Mn²⁺Mn³⁺(PO₄)O
- Mohs hardness
- 4
- Density
- 3.55 g/cm³
- Streak
- Brownish Black
- Luster
- Sub-metallic
- Transparency
- Opaque
- Crystal system
- Orthorhombic
- Crystal habit
- Massive, Granular
- Cleavage
- Distinct On {010}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Granite Pegmatites
- Typical price
- $50-300 per specimen
Where rockhounds find joosteite
Classic worldwide localities
- Jooste pegmatite, Namibia
- Otjozondjupa Region, Namibia
Field-hunting tip
Look in granite pegmatites country — that is the host setting where joosteite typically forms. If you start seeing triphylite, quartz, muscovite in float, you are in the right ground. Field specimens usually show a massive, granular habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find joosteite on the map
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