Billwiseite is a rare antimony niobium tungsten oxide. It occurs in a complex zoned granitic pegmatite of the LCT (Li-Cs-Ta) type. It was first described from Stak Nala, Karakoram Mountains, 70 km east of Gilgit, Pakistan.
Is this billwiseite?
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 billwiseite with a known reference. Billwiseite 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. Streak: colorless to very pale yellow.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: pale yellow.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: tabular crystals, crystalline aggregates.
Often confused with
Billwiseite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Billwiseite is noticeably harder (Mohs 5 vs. 2-2.5); streak differs, so Billwiseite leaves colorless to very pale yellow, Senarmontite leaves white; luster reads vitreous on Billwiseite and resinous to subadamantine on Senarmontite.
How to tell apart: Billwiseite is noticeably harder (Mohs 5 vs. 2.5-3); streak differs, so Billwiseite leaves colorless to very pale yellow, Valentinite leaves white; luster reads vitreous on Billwiseite and adamantine, pearly on cleavages on Valentinite.
Often found alongside billwiseite
Minerals reported to co-occur with billwiseite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Sb³⁺₅Nb₃WO₁₈
- Mohs hardness
- 5
- Density
- 6.330 g/cm³
- Colors
- Streak
- Colorless to very pale yellow
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Monoclinic
- Crystal habit
- Tabular crystals, crystalline aggregates
- Cleavage
- {100} indistinct
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In a complex zoned granitic pegmatite of the LCT (Li–Cs–Ta) type
Where rockhounds find billwiseite
Classic worldwide localities
- Stak Nala, Karakoram Mountains, 70 km east of Gilgit, Pakistan
Field-hunting tip
Where it forms: In a complex zoned granitic pegmatite of the LCT (Li–Cs–Ta) type. If you start seeing lepidolite, b-rich muscovite in float, you are in the right ground. Typical habit: tabular crystals, crystalline aggregates. Train your eye for that shape before scanning the outcrop.
Common questions
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Find billwiseite on the map
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