Pyromorphite is a phosphate mineral , lead chlorophosphate Pb 5 (PO 4 ) 3 Cl. It forms rare accumulations of usually green prismatic crystals in the oxidation zones of deposits of lead and lead- zinc ores .
| Pyromorphite | |
|---|---|
 Yellow pyromorphite from Australia | |
| Formula | Pb 5 (PO 4 ) 3 Cl |
| Physical properties | |
| Colour | Green, Yellow, Brown, Grayish, Yellowish Red |
| Trait color | White |
| Shine | Diamond, resinous |
| Hardness | 3,5 - 4 |
| Density | 6.7 - 7 g / cm³ |
| Syngonia | Hexagonal |
Title
In 1748 , Yu. G. Valerius called this mineral “green lead spar”. I.F. Gausman in 1813 introduced the modern name, derived from a combination of the words dr.-Greek. πῦρ - fire and other Greek μορφή is a form, since the ball formed during the melting of a mineral crystallizes as it cools .
Synonyms: green or mottled lead ore.
Physical Properties
- Color : Green, brown, less often yellow, wax-yellow, golden-honey, orange-red ("Scotland"), grayish-white, colorless, black.
- Shine : Diamond, greasy.
- Transparency : Translucent.
- Trait : White, light gray.
- Mohs hardness : 3.5-4.
- Density : 6.7-7.
- Kink : Uneven.
- Syngonia : Hexagonal .
- Crystal shape : Prismatic, needle-shaped, columnar, similar to apatite crystals, often have a barrel-shaped appearance (“em barrels”).
- Symmetry class : Hexagonal-bipyramidal - 6 / m.
- Axis ratio : s / a = 0.734.
- Cleavage : Virtually absent.
- Aggregates : Kidney-shaped, granular, bunch-shaped, dense, continuous masses, short-banded splices located parallel or radially; often overgrown, rarely with two heads; Large samples are composed of several small ones.
- Behavior in acids : Soluble in nitric acid .
It easily fuses into a ball, leaving a yellow coating on the corner.
Chemical Composition
Lead (II) oxide (PbO) 81.7%, phosphorus pentoxide (P 2 O 5 ) 15.7%, chlorine (Cl) 2.6%; impurities of calcium , arsenic and chromium .
Chemical formula: Pb 5 (PO 4 ) 3 Cl.
Associated Minerals
Galenite , cerussite , barite , anglesite , mimetizite , vanadinite , wulfenite , quartz .
Similar Minerals
Mimetisite (Pb 5 (AsO 4 ) 3 Cl), vanadinite (Pb 5 (VO 4 ) 3 Cl). In external characteristics, they are so similar to pyromorphite that they can be distinguished, as a rule, only with the help of chemical analysis.
Deposits
The secondary mineral of galena deposits. Most deposits have now been developed. Findings are known in Saxony and Rhineland ( quintal ore with thousands of crystals, often more than 3 cm), Freiberg , Annaberg , Berenstein , Johanngeorgenstadt , Bockau , Volkenstein , Ore Mountains , Clausthal in Harz , Ems , Badenweiler ( Germany ); Pribram ( Czech Republic ), Cornwall and Cumberland ( Great Britain ), Beryozovsky gold ore and Nerchinsk deposits (Middle Urals, Russia), on the island of Sardinia , ( Italy ), in Mexico .
Origin
It is formed mainly in the oxidation zone of lead and lead-zinc deposits.
Meaning and Application
Polymetallic ore . Of interest as lead ore. Together with other minerals of lead ores, it is used to extract metallic lead.