Magnesite is a magnesium carbonate mineral (hence the name) which in this massive form has a pale, off white colouration and botryoidal texture. It often forms as veins in ultramafic rocks and in both contact and regional metamorphic rocks. Modern uses of this mineral include as a lining in blast furnaces, kilns and incinerators as well as gemstone jewelry as it can be dyed. Interestingly, the mineral has also been detected in meteorites and on the planet Mars its self. Although, not the case with our samples, these mineral specimens come from Greece and are supplied in a card tray with an information label.