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

Caledonite is a very minor ore mineral of lead and copper, but its rarity makes its industrial use limited. Due to its occasionally striking crystals and vibrant color, however, caledonite has value as a collector's mineral.

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, CuPbSO4OH2

malachite, Cu2(CO3)(OH)2

cerussite, PbCO3

brochantite, Cu4(SO4)(OH)6

anglesite, PbSO4

Caledonite has one major alterative name: caledonita.

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.