Stibnite crystals, close-up. Stibnite, also called antimonite, is a sulphide of the element antimony. It is an orthorhombic, lead-grey mineral with a metallic lustre. Here it is occurring in exceptionally large columnar crystals, whereas needle-thin crystals are much more common. It is mined as a source of antimony, which is used in the electronics industry. Actual height: 24 centimetres.