The Mineral Caledonite

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Caledonite, is a rich, blue/ green sulfate–carbonate mineral of copper and lead. Its crystals have an orthorhombic structure. This rare mineral occurs in areas containing deposits of oxidized lead-copper. Basically, it’s a collector’s mineral. Though comprising of lead and copper, this secondary mineral is not known to have deposits for use as an ore. Its fully developed crystals have a deep bluish-green color suggestive of secondary copper minerals, though its sheen is like that of secondary lead minerals.

Chemical Formula
Cu2Pb5 (SO4) 3 (CO3) (OH) 6 

Derivation of Name
The Caledonite mineral derives its name from the earliest Latin/Roman term for the Highlands of Scotland, “Caledonia." That is where its first known deposits were located in the Leadhills in Strathclyde (Lanarkshire).

Occurrence
Caledonite crops up in oxidized deposits of lead-copper as a rare secondary mineral. It is frequently associated with minerals like Anglesite, Azurite, Brochantite, Cerussite, Linarite, Leadhillite, and Malachite.

Gemology
Caledonite stones are found helpful in mitigation of chills by bringing warmth to cold places and also for speeding up healing of wounds and controlling disorders of the epithelial tissues.

Source
Caledonite which is an unusual mineral, is found in the deposits of copper-lead that is oxidized. Apart from the main source, there are other places where Caledonite occurs. They are England, the United States, Iran, Russia, Australia, Chile and many others. The other minerals connected with this are Anglesite, Brochantite, Cerussite, Linarite, Malachite, Leadhillite and Azurite. Caledonite, produce a charge when it is pressurized; it is piezoelectric (electrical charge appearing on application of stress in some crystals).

Mineralogy
The simultaneous presence of anions of carbonate and sulfates makes it difficult to classify this mineral. However, it contains more sulfates, compared to carbonates and therefore, it would be more appropriate to categorize it as a sulfate. The sulfate ion is more composite with a stronger electronegative anion, compared to carbonate anion. At times, mineralogists classify minerals on the strength of their electro negativity. For the same reasons, it is not categorized among the oxides or hydroxides.

Color
It occurs in light blue, green, and blue to bluish-green color.

Density 
5.689 g/cm3

Mohs scale hardness
2.5 – 3

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