such as Cu+4Cu2+2(S2)2S2. Structure For a copper sulfide, covellite has a complicated lamellar structure, with alternating layers of CuS and Cu2S2 with copper atoms of trigonal planar (uncommon) and tetrahedral coordination respectively. The layers are connected by S-S bonds (based on Van der Waals forces) known as S2 dimers. The Cu2S2 layers only has one l/3 bond along the c-axis (perpendicular to layers), thus only one bond in that direction to create a perfect cleavage {0001}. The conductivity is greater across layers due to the partially filled 3p orbitals, facilitating electron mobility. Formation Naturally occurring Covellite is commonly found as a secondary copper mineral in deposits. Covellite is known to form in weathering environments in surficial deposits where copper is the primary sulfide. As a primary mineral, the formation of covellite is restricted to hydrothermal conditions, thus rarely found as such in copper ore deposits or as a volcanic sublimate. Synthetic Covellite's unique crystal structure is related to its complex oxidative formation conditions, as seen when attempting to synthesize covellite. Its formation also depends on the state and history of the associated sulfides it was derived from. Experimental evidence shows ammonium metavanadate (NH4VO3) to be a potentially important catalyst for covellite's solid state transformation from other copper sulfides. Researchers discovered that covellite can also be produced in the lab under anaerobic conditions by sulfate reducing bacteria at a variety of temperatures. However, further research remains, because although the abundance of covellite may be high, the growth of its crystal size is actually inhibited by physical constraints of the bacteria. It has been experimentally demonstrated that the presence of ammonium vanadates is important in the solid state transformation of other copper sulfides to covellite crystals. Occurrence Covellite's occurrence is widespread around the world, with a significant number of localities in Central Europe, China, Australia, Western United States, and Argentina. Many are found close to orogenic belts, where orographic precipitation often plays a role in weathering. An example of primary mineral formation is in hydrothermal veins at depths of 1,150 m found in Silver Bow County, Montana. As a secondary mineral, covellite also forms as descending surface water in the supergene enrichment zone oxidizes and redeposits covellite on hypogene sulfides (pyrite and chalcopyrite) at the same locality. An unusual occurrence of covellite was found replacing organic debris in the red beds of New Mexico. Nicola Covelli (1790-1829), the discoverer of the mineral,