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. Billwiseite leaves a yellow streak.
- 3Read the lusterHold the specimen under a strong light. Billwiseite typically shows a vitreous luster.
- 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. 2.5); streak differs, so Billwiseite leaves 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 yellow, Valentinite leaves white; luster reads vitreous on Billwiseite and adamantine 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
- Yellow
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Monoclinic
- Crystal habit
- Tabular Crystals, Crystalline Aggregates
- Cleavage
- {100} Indistinct
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Hydrothermal Mineralized Zones in Metamorphic Rock
Where rockhounds find billwiseite
Classic worldwide localities
- Stak Nala, Karakoram Mountains, 70 km east of Gilgit, Pakistan
Field-hunting tip
Look in hydrothermal mineralized zones in metamorphic rock country, the host setting where billwiseite typically forms. If you start seeing galena, sphalerite, annabergite in float, you are in the right ground. Field specimens usually show a tabular crystals, crystalline aggregates habit, so 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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