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.

Hardness

5-6

Mohs

Luster

Vitreous

Streak

White

Transparency

Semitransparent

mineralrareOsumilite Group family

Brannockite

Hardness: 5-6
Luster: Vitreous
Streak: White
Transparency: Semitransparent

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Is this brannockite?

5-step field check

Run through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.

1
Test the hardness
Try to scratch brannockite with a known reference. Brannockite sits at Mohs 5-6, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Streak: white.
3
Read the luster
Hold the specimen under a strong light. Luster: vitreous.
4
Match the color range
Compare against the expected color range: colorless.
5
Look at form & habit
Crystal system: hexagonal. Typical habit: prismatic crystals.

Often confused with

Brannockite vs. its common look-alikes, and how to tell them apart in the field.

mineral

Osumilite

Mohs 5-5.5

How to tell apart: Streak differs, so Brannockite leaves white, Osumilite leaves blue-gray.

How to tell apart: Beryl is the harder of the two (Mohs 7.5-8 vs. 5-6).

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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: 5-6
Density: 2.980 g/cm³
Colors: Colorless
Streak: White
Luster: Vitreous
Transparency: Semitransparent
Crystal system: Hexagonal
Crystal habit: Prismatic crystals
Cleavage: None
Fluorescence: Bright blue-white under SW UV
Rarity: Rare
Uses: Collector
Host rock: In the late hydrothermal portions of a Li-Sn-rich pegmatite, in vugs and on flat fracture surfaces

Where rockhounds find brannockite

Classic worldwide localities

Foote mine, Kings Mountain, Cleveland Co., North Carolina, USA

Field-hunting tip

Where it forms: In the late hydrothermal portions of a Li-Sn-rich pegmatite, in vugs and on flat fracture surfaces. If you start seeing bavenite, pyrite, tetrawickmanite in float, you are in the right ground. Typical habit: prismatic crystals. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify brannockite?+

Mohs hardness is 5-6. Luster: vitreous. The streak is white. Common colors include colorless.

Where is brannockite found?+

Notable localities include Foote mine, Kings Mountain, Cleveland Co., North Carolina, USA.

What rocks look like brannockite?+

Brannockite is most often confused with Osumilite, Sugilite, Beryl. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with brannockite?+

Brannockite commonly co-occurs with Bavenite, Pyrite, Tetrawickmanite, Stannian titanite, Albite, Quartz. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does brannockite form in?+

Where it forms: In the late hydrothermal portions of a Li-Sn-rich pegmatite, in vugs and on flat fracture surfaces. Working float back to the host body is the standard way to chase a fresh occurrence.

What is brannockite used for?+

Brannockite is used in collector.

Find brannockite on the map

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