Corkite

A lead-iron phosphate mineral, a member of the Beudantite group.

Can form gemmy micro crystals, which are of interest to micromineral collectors.

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Information about Corkite

Corkite is a rare secondary lead iron phosphate sulphate belonging to the beudantite group – a family of complex secondary phosphate-sulphate minerals that forms in the oxidised zones of lead-bearing ore deposits.

It is the phosphate-dominant member of a series with beudantite (arsenate-dominant), with which it forms a continuous compositional series; pure end-member corkite contains phosphate rather than arsenate as the dominant anion alongside sulphate.

It typically forms as small rhombohedral or pseudocubic crystals with a vitreous to resinous lustre, in colours ranging from pale yellow to green, olive-green, brownish, or colourless. Individual crystals are usually small – a few millimetres at most – and occur as coatings, drusy crusts, or individual crystals on gossan or iron-oxide-rich matrix. The combination of rhombohedral crystal form, moderate lustre, and lead-bearing gossan environment is characteristic, though definitive identification from beudantite requires chemical analysis.

The beudantite group minerals as a whole are a classic product of the oxidised zones of lead-zinc-copper polymetallic sulphide deposits, and several members – including beudantite, corkite, hinsdalite, and plumbojarosite – occur together at the same localities.

 

Uses and History

Corkite has no industrial applications and is collected purely as a mineralogical specimen.

The mineral was named in 1869 by Gilbert-Joseph Adam from the type locality, the Glandore Mines, Glandore, Cork County, Munster, Ireland. Obviously, the mineral is named after the county rather than the specific mine.

 

 

Mineralogy

Chemistry
A lead iron phosphate sulphate hydroxide of the beudantite group, formula PbFe3+3(PO4)(SO4)(OH)6. Phosphate-dominant series with beudantite (arsenate); intermediate compositions are common.
Colours and Variations
Pale yellow to yellowish-green, olive-green, brown, or colourless; colour varies with composition and impurities
Streak
Lustre
Vitreous to resinous
Transparency
Transparent to translucent
Fracture
Tenacity
Crystal habit
Rhombohedral to pseudocubic crystals; drusy crusts; coatings on gossan matrix
Crystal system
Trigonal
Mohs hardness
3.5–4.5
Fluorescence
Non-fluorescent
Specific Gravity
4.295–4.31
Easiest testing method
Rhombohedral crystal form, relatively high specific gravity for a yellow to green mineral, and occurrence in lead-bearing oxidised gossan are characteristic of the beudantite group. Distinguishing corkite from beudantite (arsenate-dominant) and intermediate compositions requires chemical analysis or X-ray diffraction. No effervescence with acid distinguishes it from lead carbonates (cerussite).

Hazards and Warnings

Toxic mineral: contains lead. Lead is a serious cumulative toxin. Wash hands thoroughly after handling, avoid inhaling dust, and keep specimens away from children and food preparation areas.

Almost all rocks, minerals (and, frankly, almost all other substances on earth) can produce toxic dust when cutting, which can cause serious respiratory conditions including silicosis. When cutting or polishing rocks, minerals, shells, etc, all work should be done wet to minimise the dust, and a suitable respirator or extraction system should be used.

 

Translations

Arabic:

Hindi:

Portuguese:

  • Corcita

Bengali:

Indonesian:

Punjabi:

English:

  • Corkite

Italian:

Russian:

  • Коркит

French:

Japanese:

Spanish:

  • Corkita

German:

  • Corkit

Korean:

Thai:

Gujurati:

Mandarin Chinese:

Urdu:

 

Further Reading / External Links