Holtstamite is a rare calcium-manganese aluminum garnet species discovered in the Wessels Mine of the Kalahari Manganese Field. It typically occurs as small, anhedral grains within manganese ore, requiring laboratory analysis to distinguish it from more common garnets like grossular. It is a highly sought-after specimen for specialized garnet collectors due to its restricted type locality.
Is this holtstamite?
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 holtstamite with a known reference. Holtstamite sits at Mohs 6, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: white.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: brownish yellow.
- 5Look at form & habitCrystal system: tetragonal. Typical habit: inclusions.
Often confused with
Holtstamite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside holtstamite
Minerals reported to co-occur with holtstamite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ca₃Al₂(SiO₄)₂(OH)₄
- Mohs hardness
- 6
- Density
- 3.25 g/cm³
- Colors
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Tetragonal
- Crystal habit
- Inclusions
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector, Scientific research
- Host rock
- In a manganese-rich calc-silicate contact metamorphic rock
Where rockhounds find holtstamite
Classic worldwide localities
- Wessels mine, Kalahari manganese field, South Africa
Field-hunting tip
Where it forms: In a manganese-rich calc-silicate contact metamorphic rock. If you start seeing calcite, henritermierite in float, you are in the right ground. Typical habit: inclusions. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify holtstamite?+
Where is holtstamite found?+
What rocks look like holtstamite?+
What minerals are found with holtstamite?+
What kind of rock does holtstamite form in?+
What is holtstamite used for?+
Find holtstamite on the map
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