Large cabinet specimen of azurite and malachite. The contrast of the intensely blue azurite clusters and encrusting malachite makes this a really beautiful and fascinating piece. Lots of little crystal-filled vugs and a vein of malachite exposed as a delicate plate on one side.
Likely collected in the early-1990s, this is a great example of the highest quality deposits of these minerals. Azurite [Cu3(CO3)2(OH)2] is a hydrated copper carbonate mineral typically formed in the shallow crust on the edges of more pure copper ore bodies. It, and its "sister" mineral, malachite [Cu2CO3(OH)2], are typically found in close association with one another - which makes sense if you look at how similar their formulas are; they are chemically identical, just structured differently! They also can only form when there is available water; we don't find dehydrated copper carbonate [CuCo3] in nature because of how easily the copper anion dissolves in water. The vibrant blues and greens in these minerals are created by the way light interacts with the copper anions in the mineral - transition metals, of which Cu is one, interact with and absorb specific wavelengths of light due to the way their electrons are arranged; in this case, copper absorbs different portions of the visible light spectrum due to the different crystal structures of the two minerals.
