Hedenbergite is an iron-bearing mineral belonging to the pyroxene group, where it is the iron rich end member. Its chemical formula is CaFeSi2O6. It only rarely occurs in pure form and is sometimes synthesized in the lab for scientific purposes. In nature it is usually found in metamorphic rocks, well developed crystals having a blocky habitat in dull grey to black colours. This specimen is from Nordmarken, Sweden, where it is associated with iron ore deposits. Actual width is 150 mm.