Is a manganese carbonate mineral with formula MnCO3 . And hardness of 3-4.Very rare in gem quality, mostly is found in parallel or concentric layers (stalactite) as hydrothermal deposit; today the biggest production comes from old abandoned silver mines in Capillitas,Catamarca,Argentina. Handle with care and avoid acid.
This piece comes from a recent deposit in China. The stone has several visible inclusions.