Hydroxylherderite is a rare beryllium phosphate mineral typically found in granitic pegmatites. Collectors prize it for its excellent, often gemmy, orthorhombic-like monoclinic crystals and its characteristically strong yellow-green fluorescence under short-wave ultraviolet light.
Is this hydroxylherderite?
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 hydroxylherderite with a known reference. Hydroxylherderite sits at Mohs 5-5.5, 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 to subvitreous, resinous.
- 4Match the color rangeCompare against the expected color range: colorless, blue, blue green, greenish white, white.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: prismatic crystals, blocky crystals, sometimes massive.
Often confused with
Hydroxylherderite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside hydroxylherderite
Minerals reported to co-occur with hydroxylherderite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- CaBe(PO₄)(OH)
- Mohs hardness
- 5-5.5
- Density
- 2.95 g/cm³
- Streak
- White
- Luster
- Vitreous to subvitreous, resinous
- Transparency
- Transparent to translucent
- Crystal system
- Monoclinic
- Crystal habit
- Prismatic crystals, blocky crystals, sometimes massive
- Cleavage
- On {110}, irregular
- Fluorescence
- Yellow-white under SW UV
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A late-stage mineral in miarolitic cavities in complex granite pegmatites, of hydrothermal or probable pneumatolytic origin; may form from the alteration of beryl or beryllonite
Where rockhounds find hydroxylherderite
Classic worldwide localities
- Paris, Hebron, Greenwood, Stoneham, and Newry, Oxford Co., at Topsham, Sagadahoc Co., Poland and Auburn, Androscoggin Co., Maine, USA
- Fletcher and Palermo #1 mines, near North Groton, Grafton Co., and at the Keyes mine, Orange, Grafton Co., New Hampshire, USA
- Blue Chihuahua pegmatite, near Oak Grove, San Diego Co., California, USA
- Epprechtstein and Waldheim quarries, Fichtelgebirge, Bavaria, Germany
- Viitaniemi pegmatite, near Eräjärvi, Finland
- Mursinsk, Ural Mountains, Russia
Field-hunting tip
Where it forms: A late-stage mineral in miarolitic cavities in complex granite pegmatites, of hydrothermal or probable pneumatolytic origin; may form from the alteration of beryl or beryllonite. If you start seeing elbaite, topaz, cassiterite in float, you are in the right ground. Typical habit: prismatic crystals, blocky crystals, sometimes massive. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify hydroxylherderite?+
Where is hydroxylherderite found?+
Is hydroxylherderite safe to handle?+
What rocks look like hydroxylherderite?+
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Find hydroxylherderite on the map
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