Pyrrhotite

Pyrrhotite is an unusual iron sulfide mineral in the niccolite group with up to 20% variable amounts of iron and or sulfur. Pyrrhotite is also called magnetic pyrite because the color is similar to pyrite and it is weakly magnetic. The magnetism increases as the iron content decreases. Pyrrhotite has two forms. When Pyrrhotite is low in sulfur and the formula is closer to true iron sulfide(FeS), then the structure is hexagonal. But when it is high in sulfur, the structure is monoclinic. Pyrrhotite is found with pentlandite in basic igneous rocks, veins and metamorphic rocks. It is also often found with pyrite, marcasite and magnetite.

Pyrrhotite is weakly magnetic. It is the second most common magnetic mineral. (magnetite is the most common). It has varying magnetic powers. The strength depends upon the number of iron atom vacancies in the crystal structure. Many specimens may not show evidence of magnetism but the best test to try is to see if it will attract a small paper clip, needle on a string or even move a compass needle. A related species with no iron atom vacancies (and therefore non-magnetic), is called troilite and has been found in meteorites and rarely on earth .Massive Pyrrhotite is common and magnetism is sometimes the only way to distinguish it from other brassy colored sulfides such as chalcopyrite, pyrite, pentlandite or marcasite.

Nice Pyrrhotite hexagonal crystals are rare and should highly be treasured. Quality specimens of this mineral are very difficult to find and are very expensive. Some of the nicest come from Dal'negorsk in Russia. Dal'negorsk, also known as Tetyukhe, is a famous mining region in the Kavalerovo Mining District, Primorskiy Kray, Far-Eastern Region, Russia, which is about 300 km north east of Vladivostok. The name "Tetyukhe" (which means "valley of the wild boars") is the old Chinese name for Dal'negorsk. You may find some specimens with old mineral labels with the locale listed as Tetyukhe. It was formerly known from its founding in 1897 as Tetyukhe until it was renamed Dal'negorsk in 1972.