Selwynite is a rare sodium potassium beryllium phosphate. Associated minerals include wardite, eosphorite and montmorillonite. It was first described from a quarry 0.5 km east of Wycheproof, Victoria, Australia.
Is this selwynite?
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 selwynite with a known reference. Selwynite 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. Selwynite leaves a pale lavender streak.
- 3Read the lusterHold the specimen under a strong light. Selwynite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: deep purplish blue.
- 5Look at form & habitCrystal system: tetragonal. Typical habit: massive.
Often confused with
Selwynite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside selwynite
Minerals reported to co-occur with selwynite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- NaKBeZr₂(PO₄)₄·2H₂O
- Mohs hardness
- 4
- Density
- 2.94 g/cm³
- Colors
- Streak
- Pale Lavender
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Tetragonal
- Crystal habit
- Massive
- Cleavage
- Perfect
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Hydrothermally Altered Greenstone
Where rockhounds find selwynite
Classic worldwide localities
- Heathcote, Victoria, Australia
Field-hunting tip
Look in hydrothermally altered greenstone country, the host setting where selwynite typically forms. If you start seeing quartz, chromite, albite in float, you are in the right ground. Field specimens usually show a massive habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify selwynite?+
Where is selwynite found?+
What rocks look like selwynite?+
What minerals are found with selwynite?+
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What is selwynite used for?+
Find selwynite on the map
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