Holtite is a very rare tantalum-rich borosilicate mineral first discovered in Australian pegmatites. It typically occurs as yellowish to brownish fibrous or prismatic crystals embedded in quartz or muscovite matrices. Because it is chemically related to dumortierite but contains significant tantalum, it is highly sought after by advanced mineral collectors.
Is this holtite?
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 holtite with a known reference. Holtite sits at Mohs 7-8 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Holtite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Holtite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: yellow, brown, tan, white.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: fibrous, prismatic, massive.
Often confused with
Holtite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside holtite
Minerals reported to co-occur with holtite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (Al,Ta,Sb,□)₇(SiO₄)₃(O,OH)₃
- Mohs hardness
- 7-8
- Density
- 3.8-3.9 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Orthorhombic
- Crystal habit
- Fibrous, Prismatic, Massive
- Cleavage
- Distinct On {110}
- Rarity
- Rare
- Uses
- Collector, Mineralogical Study
- Host rock
- Pegmatites
- Typical price
- $50-500 thumbnail
Where rockhounds find holtite
Classic worldwide localities
- Greenbushes, Western Australia
- Londonderry, Western Australia
- Hurn, Czech Republic
Field-hunting tip
Look in pegmatites country — that is the host setting where holtite typically forms. If you start seeing quartz, muscovite, tantalite in float, you are in the right ground. Field specimens usually show a fibrous, prismatic, massive habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify holtite?+
Where is holtite found?+
How much is holtite worth?+
What rocks look like holtite?+
What minerals are found with holtite?+
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Find holtite on the map
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