Hydroxylgugiaite is an extremely rare beryllium-bearing silicate primarily found in the volcanic ejecta of the Eifel region in Germany. It typically occurs as small, transparent prismatic crystals within cavities of metamorphosed limestone xenoliths. Due to its scarcity and association with complex mineral assemblages, it is highly sought after by specialized systematic mineral collectors.
Is this hydroxylgugiaite?
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 hydroxylgugiaite with a known reference. Hydroxylgugiaite 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. Hydroxylgugiaite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Hydroxylgugiaite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: colorless, white.
- 5Look at form & habitCrystal system: tetragonal. Typical habit: prismatic crystals.
Often confused with
Hydroxylgugiaite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside hydroxylgugiaite
Minerals reported to co-occur with hydroxylgugiaite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ca₂BeSi₂O₇(OH)₂
- Mohs hardness
- 5
- Density
- 2.89 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Tetragonal
- Crystal habit
- Prismatic Crystals
- Cleavage
- Distinct On {001}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Metamorphic Carbonate Xenoliths in Volcanic Rocks
- Typical price
- $50-300 per specimen
Where rockhounds find hydroxylgugiaite
Classic worldwide localities
- Caspar quarry, Ettringen, Eifel, Germany
- Bellerberg Volcano, Eifel, Germany
Field-hunting tip
Look in metamorphic carbonate xenoliths in volcanic rocks country — that is the host setting where hydroxylgugiaite typically forms. If you start seeing ettringite, thaumasite, afwillite in float, you are in the right ground. Field specimens usually show a prismatic crystals habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify hydroxylgugiaite?+
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What rocks look like hydroxylgugiaite?+
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Find hydroxylgugiaite on the map
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