Picropharmacolite
A variety of Minerals
What is Picropharmacolite?
Picropharmacolite, Ca4Mg(AsO3OH)2(AsO4)2·11H2O, is a rare arsenate mineral. It was named in 1819 from the Greek for bitter, in allusion to its magnesium content, and its chemical similarity to pharmacolite. The mineral irhtemite, Ca4Mg(AsO3OH)2(AsO4)2·4H2O, has the same composition as picropharmacolite, except that it has only four water molecules per formula unit, instead of eleven. It may be formed by the dehydration of picropharmacolite.
Market Value Factors
Pricing varies for every rock and mineral, so use these universal factors to gauge Picropharmacolite before comparing listings or appraisals.
Size & Weight
Larger, intact specimens usually command higher prices.
Rarity & Demand
Scarce material or popular varieties sell at a premium.
Condition & Finish
Chips, repairs, and heavy wear lower value; clean prep helps.
Treatment & Provenance
Untreated specimens with documented locality are prized.
Picropharmacolite Localities Map
See where Picropharmacolite is found with a localities map, collecting zones, and geology context. Generate a sample map preview below.
Key Characteristics
Composition of Picropharmacolite
Infrared spectra show that picropharmacolite contains water molecules H2O, hydroxyl groups (OH) co-ordinated with Mg cations, and acid arsenate radicals (HAsO4). There are strong structural similarities with guerinite, Ca5(AsO3OH)2(AsO4)2.9H2O which indicates a similar formula for the two minerals. X-ray diffraction methods indicate that As, Ca and Mg cations are positioned in corrugated layers parallel to the c axis, the layers being linked by hydrogen bonding only. Four independent water molecules are sandwiched between adjacent layers, and build up hydrogen-bonded chains which are also parallel to the c axis. The ratio of four Ca to one Mg remains fairly steady, and no significant Ca/Mg substitution occurs in any cation site. Hence if the formula of picropharmacolite is written as Ca4Mg(H2O)7(AsO3OH)2(AsO4)2.4H2O, it is a better representation of the structure than the more usual formula Ca4Mg(AsO3OH)2(AsO4)2.11H2O.
Quick Facts
Physical Properties
- Color
- White; colorless in transmitted light.
- Hardness (Mohs)
- 1 - 2
- Density
- 2.58 g/cm³
- Streak
- White
Chemical Properties
- Chemical Formula
- Ca4Mg(AsO4)2(HAsO4)2 · 11H2O
- Elements
- As, Ca, H, Mg, O
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Picropharmacolite FAQs
How do I identify Picropharmacolite?
Picropharmacolite can be identified by its hardness of 1 - 2 on the Mohs scale, White; colorless in transmitted light. color. Look for these key characteristics when examining specimens.
What color is Picropharmacolite?
Picropharmacolite typically appears in White; colorless in transmitted light.. Color can vary depending on impurities and formation conditions.
How hard is Picropharmacolite?
Picropharmacolite has a hardness of 1 - 2 on the Mohs scale. This makes it a soft mineral that can be scratched easily.
What is the composition of picropharmacolite of Picropharmacolite?
Infrared spectra show that picropharmacolite contains water molecules H2O, hydroxyl groups (OH) co-ordinated with Mg cations, and acid arsenate radicals (HAsO4). There are strong structural similarities with guerinite, Ca5(AsO3OH)2(AsO4)2.9H2O which indicates a similar formula for the two minerals. X-ray diffraction methods indicate that As, Ca and Mg cations are positioned in corrugated layers parallel to the c axis, the layers being linked by hydrogen bonding only. Four independent water molecules are sandwiched between adjacent layers, and build up hydrogen-bonded chains which are also parallel to the c axis. The ratio of four Ca to one Mg remains fairly steady, and no significant Ca/Mg substitution occurs in any cation site. Hence if the formula of picropharmacolite is written as Ca4Mg(H2O)7(AsO3OH)2(AsO4)2.4H2O, it is a better representation of the structure than the more usual formula Ca4Mg(AsO3OH)2(AsO4)2.11H2O.
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