Rhodochrosite

Rhodochrosite

The name Rhodochrosite is derived from the greek word, rhodos, for rose red.  It is a calcite based mineral.

Typically, Rhodochrosite is a combination of minerals as 100% Rhodochrosite is red.  It's pretty rare to find it this way though.  More usual are striations of red, deep to light pink, tan to brown, and white.  It ranges from nearly transparent to opaque.  

Another crystal, Rhodonite, is also pink to deep rose, but Rhodonite usually has a good bit of black in its appearance and is a much harder mineral than Rhodochrosite.  Because Rhodochrosite is so soft, it is quite challenging to facet for jewelery.

Rhodochrosite contains siderite (iron carbonate), but when calcium is present, it replaces the siderite which changes some of the red in the rhodochrosite to white, accounting for all the various shades of pink that are more commonly mined.

It's common for Rhodochrosite to occur as veins in rock and often crystallizes alongside silver.  In Argentina, there is a 700 year old Incan silver mine where the rock is full of manganese that has stalactites and stalagmites of Rhodochrosite.  As the water dripped through the manganese filled rocks to form the stalagtites and stalagmites, it crystallized as Rhodochrosite.  When the stalactites and stalagmites are removed and sliced, they yield gorgeous examples of Rhodochrosite that has a center of red or pink and rings of white and pink.

A lot of Rhodochrosite is mined in Colorado, Argentina, Peru and South Africa.  It is the official gemstone of Colorado and Argentina.  The Sweet Home mine in Colorado produces some of the finest, largest and most transparent specimens.  

Sometimes, as a result of Rhodochrosite being exposed to air, a fine layer of film of manganese oxididates on its surface which can make it darker.

Rhodochrosite can also transforms into one of the black manganese oxides, such as Psilomelane.