Rhodochrosite

Rhodochrosite is a manganese carbonate mineral which is thought to have biological help forming and the manganese comes from seawater. Crazy!

It is always pink but calcium and iron can occur with it and create different color minerals around it. Crystals are very rare but they do happen. More often banded masses form or stalactite like formations. The lighter colored bands contain more calcite. 

Most rhodochrosite is carved or turned into jewelry, a small amount of clear crystals are faceted. Rhodochrosite is formed from manganese rich sea sediment going through a metamorphic process and much of it is mined from silver mines. 

Rhodochrosite is rather soft at 3.5-4.5 on the mohs scale and often stabilized.