Marmatite blende from the Madan mine (Bulgaria) year 1995.
Dimensions of the stone: L: 55mm x W: 37mm x H: 45mm x weight: 163g.
Marmatite blende is a variety of sphalerite.
Sphalerite is mainly composed of zinc sulphide (ZnS), but marmatite is a form of sphalerite rich in iron, which gives it a darker colour. It contains zinc sulphide (ZnS) and iron, often represented by the chemical formula (Zn,Fe)S.
The presence of iron gives marmatite a colour ranging from dark brown to black.
On the Mohs scale, the hardness of marmatite varies between 3.5 and 4.
The density of marmatite is generally higher than that of pure sphalerite due to the presence of iron.