Search results
Results from the WOW.Com Content Network
The mineral marcasite, sometimes called "white iron pyrite", is iron sulfide (FeS 2) with orthorhombic crystal structure. It is physically and crystallographically distinct from pyrite, which is iron sulfide with cubic crystal structure. Both structures contain the disulfide S 2 2− ion, having a short bonding distance between the sulfur atoms.
Marcasite jewellery is jewellery made using cut and polished pieces of pyrite (fool's gold) as gemstone, and not, as the name suggests, from marcasite. [1] Both pyrite and marcasite are chemically iron sulfide, but differ in their crystal structures, giving them different physical properties. Pyrite is more stable and less brittle than marcasite.
Arsenopyrite has a related structure with heteroatomic As–S pairs rather than S-S pairs. Marcasite also possesses homoatomic anion pairs, but the arrangement of the metal and diatomic anions differs from that of pyrite. Despite its name, chalcopyrite (CuFeS 2) does not contain dianion pairs, but single S 2− sulfide anions.
Iron(II) selenide occurs naturally as the NiAs-structure mineral achavalite. More selenium rich iron selenide phases are the γ phases (γ and γˈ), assigned the Fe 3 Se 4 stoichiometry, and FeSe 2, which occurs as the marcasite-structure natural mineral ferroselite, or the rare pyrite-structure mineral dzharkenite.
Extended Wulff constructions refers to a number of different ways to model the structure of nanoparticles as well as larger mineral crystals, and as such can be used to understand both the shape of certain gemstones or crystals with twins.as well as in other areas such as how nanoparticles play a role in the commercial production of chemicals using heterogeneous catalysts.
These include ε-FeOOH, which has an orthorhombic crystal structure, [10] a cubic pyrite-type polymorph with [11] or without losing hydrogen [12] and an ultradense hexagonal structure. [13] Goethite has the same crystal structure as diaspore, the analogous aluminium oxide-hydroxide mineral. Oxygen and hydroxide ions form a hexagonal close ...
Drawings are available showing their presence in marcasite, gold, silver, copper and diamond. New mineral forms with a fiveling structure continue to be found, for instance pentagonite, whose structure was first decoded in 1973, is named because it is often found with the five-fold twinning. [2] [15]
Its crystal structure is called the wurtzite crystal structure, to which it lends its name. This structure is a member of the hexagonal crystal system and consists of tetrahedrally coordinated zinc and sulfur atoms that are stacked in an ABABABABAB pattern. The unit cell parameters of wurtzite are (-2H polytype): [7] a = b = 3.81 Å = 381 pm; c ...