Caledonite

Caledonite (green) on cerussite

General
Category| Sulfate minerals
Formula
(repeating unit)| Cu2Pb5(OH)6CO3(SO4)3
Strunz classification| 7.BC.50
Crystal system| Orthorhombic
Crystal class| Pyramidal (mm2)
(same H-M symbol)
Space group| Pmn21
Unit cell| a = 20.089(7) Å,
b = 7.146(3) Å,
c = 6.56 Å; Z = 2
Identification
Color| Blue; green
Crystal habit| Typically striated prismatic or tabular crystals; radial aggregates
Cleavage| [001] perfect; [100] distinct
Fracture| Uneven
Tenacity| Brittle
Mohs scale hardness| 2.5–3
|re|er}}| Vitreous
Streak| Green-white; blue-green
Diaphaneity| Transparent to translucent
Specific gravity| 5.6–5.8
Optical properties| Biaxial (−)
Refractive index| nα = 1.818(3) nβ = 1.866(3) nγ = 1.909(3)
Birefringence| δ = 0.091
Pleochroism| Weak
2V angle| Measured: 85°
References| [1][2][3][4]

Caledonite, whose name derives from Caledonia, the historical name of its place of discovery (Scotland), is a richly colored blue-green sulfate-carbonate mineral of lead and copper with an orthorhombic crystal structure. It is an uncommon mineral found in the oxidized zones of copper-lead deposits.

## Contents

* 1 Collectible properties
* 2 Associated minerals
* 3 Notes for identification
* 4 References

## Collectible properties

Caledonite's primary use is a collector's mineral. Although it contains copper and lead, it is a secondary mineral and is not prevalent enough in any known deposits to be used as an ore. Caledonite, when developed into full crystals, can have a deep blue-green color reminiscent of secondary copper minerals. Its high lustre, on the other hand, is more like secondary lead minerals. Localities in which caledonite occurs as well developed crystals are quite rare and include the Mammoth-St. Anthony Mine at Tiger, Arizona, a few mines in California, such as the Reward Mine. A few other mines in Arizona and Chile have been known to produce samples.

## Associated minerals

Given that caledonite is found in oxidized copper/lead deposits, it is frequently found in association with other copper and lead minerals. Frequently associated minerals include: linarite, malachite, cerussite, brochantite, anglesite, leadhillite, and azurite.[2]

## Notes for identification

Caledonite's blue color is a useful indicator, but insufficient, especially since one of its associates, linarite, is a vivid blue as well. Useful tests for determining if a specimen is caledonite include its density, streak, and crystal habit.

## References

1. ↑ Mineralienatlas
2. ↑ 2.0 2.1 "Handbook of Mineralogy". http://www.handbookofmineralogy.com/pdfs/caledonite.pdf.
3. ↑ MinDat Listing
4. ↑ Webmineral Listing
5. ↑ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine 85 (3): 291–320. doi:10.1180/mgm.2021.43. Bibcode: 2021MinM...85..291W.

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