Picropharmacolite is a rare calcium-magnesium arsenate that typically forms delicate, silky acicular tufts or crusts in oxidized mineral deposits. Due to its fragility and mineralogical rarity, it is highly prized by advanced collectors of secondary arsenate species.
Is this picropharmacolite?
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 picropharmacolite with a known reference. Picropharmacolite sits at Mohs 1.5-2, 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: feeble pearly to silky.
- 4Match the color rangeCompare against the expected color range: colorless, silky white.
- 5Look at form & habitCrystal system: triclinic. Typical habit: botryoidal, fibrous, radial.
Often confused with
Picropharmacolite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Luster reads feeble pearly to silky on Picropharmacolite and vitreous, pearly on cleavages on Pharmacolite.
How to tell apart: Luster reads feeble pearly to silky on Picropharmacolite and vitreous; pearly on cleavages on Haidingerite.
Often found alongside picropharmacolite
Minerals reported to co-occur with picropharmacolite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ca₄Mg(AsO₄)₂(AsO₃OH)₂·11H₂O
- Mohs hardness
- 1.5-2
- Density
- 2.62 g/cm³
- Colors
- ColorlessSilky white
- Streak
- White
- Luster
- Feeble pearly to silky
- Transparency
- Semitransparent
- Crystal system
- Triclinic
- Crystal habit
- Botryoidal, fibrous, radial
- Cleavage
- {100}, {010}, perfect
- Fluorescence
- Blue-white under SW UV; Blue-white under LW UV
- Rarity
- Rare
- Uses
- Collector
- Host rock
- An oxidation product of arsenic-bearing sulfides in reaction with surrounding calcic rocks; a recent efflorescence in mine workings
Where rockhounds find picropharmacolite
Classic worldwide localities
- Sterling Hill, Ogdensburg, Sussex Co., New Jersey, USA
- Long fibers at the Getchell mine, Potosi district, Humboldt Co., Nevada, USA
- Richelsdorf, Hesse, Germany
- Freiberg, Marienberg, Annaberg, and Schneeberg, Saxony, Germany
- Anton mine, Heubachtal, near Schiltach, and at Wittichen, Black Forest, Germany
- Sainte-Marie-aux-Mines, Haut-Rhin, France
Field-hunting tip
Where it forms: An oxidation product of arsenic-bearing sulfides in reaction with surrounding calcic rocks; a recent efflorescence in mine workings. If you start seeing erythrite, pharmacolite in float, you are in the right ground. Typical habit: botryoidal, fibrous, radial. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify picropharmacolite?+
Where is picropharmacolite found?+
Is picropharmacolite safe to handle?+
What rocks look like picropharmacolite?+
What minerals are found with picropharmacolite?+
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Find picropharmacolite on the map
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