Large amounts of limonite can be produced by alteration of this mineral and it lends its name to a geometric form which is one of its two common crystal habits.
Large amounts of limonite can be produced by alteration of this mineral and it lends its name to a geometric form which is one of its two common crystal habits. Its oxidation plays an important role in the supergene alteration of hydrothermal sulfide deposits. Other features include penetration twins known as "iron crosses" as well as characteristic 3-fold rotational symmetry-related striations on crystal faces. Its polymorph marcasite features a distinctive (*) cockscomb shape and this mineral has a distinctive greenish black streak. It is also the most common sulfide mineral, occurring in almost all hydrothermal deposits. For 10 points, name this often cubic brassy-yellow mineral with the formula FeS2, commonly known as "fool's gold".
Large amounts of limonite can be produced by alteration of this mineral and it lends its name to a geometric form which is one of its two common crystal habits.
{pyrite} [accept {fool’s gold} before read, accept {FeS2} before mentioned]