Brannockite is an extremely rare zirconium silicate mineral belonging to the osumilite group. It typically appears as small, colorless to pale yellow prismatic crystals and is primarily sought after by advanced collectors of rare minerals.
Is this brannockite?
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 brannockite with a known reference. Brannockite sits at Mohs 5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Brannockite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Brannockite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: colorless, white, pale yellow.
- 5Look at form & habitCrystal system: hexagonal. Typical habit: prismatic crystals.
Often confused with
Brannockite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Brannockite leaves white, Osumilite leaves blue-gray.
How to tell apart: Sugilite is the harder of the two (Mohs 6-6.5 vs. 5).
How to tell apart: Beryl is the harder of the two (Mohs 7.5-8 vs. 5).
Often found alongside brannockite
Minerals reported to co-occur with brannockite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- KSn₂(Li₃Si₁₂)O₃₀
- Mohs hardness
- 5
- Density
- 2.98 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Hexagonal
- Crystal habit
- Prismatic Crystals
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Alkaline Igneous Rocks
Where rockhounds find brannockite
Classic worldwide localities
- Foote Mineral Co. mine in Kings Mountain, Cleveland County., North Carolina, USA
Field-hunting tip
Look in alkaline igneous rocks country, the host setting where brannockite typically forms. If you start seeing pectolite, quartz, aegirine in float, you are in the right ground. Field specimens usually show a prismatic crystals habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find brannockite on the map
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