Pyrite (small groups 50 to 200 grams) of the highest quality with large crystals.

Pyrite, also known as iron molar, is a mineral with the chemical formula FeS2, or iron disulfide. This mineral is an important source of iron and sulfur. It often crystallizes in well-formed, euhedral cubes with characteristic striations and a goldish luster. It is also known as 'tinsel' or 'fool's gold' because it has sometimes been confused with gold. The term 'cat's gold' is sometimes used incorrectly, but this actually refers to yellow mica or resin. Because pyrite is common, it can give the illusion of great wealth, although it is not very valuable (although it can be sold). Pyrite is found in the company of other sulphurous minerals and oxides, in quartz veins, sedimentary rocks in coal seams and as a substitute mineral in fossils. Pyrite is a disulfide with sulfur pairs (S2)2- and Fe2+ ions, surrounded by an octahedral structure in a t2g6 low spin state. Since both ions have a closed configuration, it is a diamagnetic semiconductor. When pyrite weathers, iron (hydr)oxides are formed and sulfuric acid is released. This acid can react with other minerals, leading to the formation of minerals such as gypsum, alunite and jarosite. A well-known location for pyrite is the island of Elba. The name 'pyrite' is derived from the ancient Indo-European word 'pyr' (fire), comparable to 'pyrotechnics' (the art of fireworks) or the English 'pyre' (funeral pyre), because sparks could be struck by burning pyrite against to strike flint or iron. Nowadays 'flint' means something completely different, namely a form of SiO2. Other names for pyrite include ferrous sulfide, sulfuric iron, and the less common terms iron blende and iron molar. Pyrite was sometimes sold as fake gold in the past because of its gold-like luster. However, this shine changes when the surface tilts, while with real gold the shine remains constant.