Hylbrownite is a rare sodium magnesium phosphate that forms colorless to white sprays of thin prismatic to acicular crystals. It is a secondary mineral in the oxidized zone of a polymetallic sulfide deposit. It was first described from the Dome Rock mine, Olary Province, South Australia, Australia.
Is this hylbrownite?
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 hylbrownite with a known reference. Hylbrownite sits at Mohs 3-3.5, 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: vitreous.
- 4Match the color rangeCompare against the expected color range: colorless, white.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: sprays of thin prismatic to acicular crystals.
Often confused with
Hylbrownite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Hylbrownite leaves white, Pentlandite leaves pale bronze-brown; luster reads vitreous on Hylbrownite and metallic on Pentlandite.
How to tell apart: Streak differs, so Hylbrownite leaves white, Pyrrhotite leaves dark grayish black; luster reads vitreous on Hylbrownite and metallic on Pyrrhotite.
Often found alongside hylbrownite
Minerals reported to co-occur with hylbrownite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Na₃MgP₃O₁₀·12H₂O
- Mohs hardness
- 3-3.5
- Density
- 1.81 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Monoclinic
- Crystal habit
- Sprays of thin prismatic to acicular crystals
- Cleavage
- Good parallel {001} and {100}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A secondary mineral in the oxidized zone of a polymetallic sulfide deposit
Where rockhounds find hylbrownite
Classic worldwide localities
- Dome Rock mine, Boolcoomatta Reserve, 42 km north of Mingary railway siding and ~470 km northeast of Adelaide, Olary Province, South Australia, Australia
Field-hunting tip
Where it forms: A secondary mineral in the oxidized zone of a polymetallic sulfide deposit. If you start seeing conichalcite, chrysocolla, cuprite in float, you are in the right ground. Typical habit: sprays of thin prismatic to acicular crystals. Train your eye for that shape before scanning the outcrop.
Common questions
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Find hylbrownite on the map
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