Russian imperial statesman. Less common species Calcium in X site Goldmanite: Kimzeyite: Morimotoite: Schorlomite: Hydroxide bearing – calcium in X site Hydrogrossular: Hibschite: (where x is between 0.2 and 1.5) Katoite: (where x is greater than 1.5) Magnesium or manganese in X site Knorringite: Majorite: Calderite: Knorringite Knorringite is a magnesium-chromium garnet species with the formula Mg3Cr2(SiO4)3. Pure endmember knorringite never occurs in nature. Pyrope rich in the knorringite component is only formed under high pressure and is often found in kimberlites. It is used as an indicator mineral in the search for diamonds. Garnet structural group Formula: X3Z2(TO4)3 (X = Ca, Fe, etc., Z = Al, Cr, etc., T = Si, As, V, Fe, Al) All are cubic or strongly pseudocubic. IMA/CNMNC – Nickel-Strunz – Mineral subclass: 09.A Nesosilicate Nickel-Strunz classification: 09.AD.25 References: Mindat.org; mineral name, chemical formula and space group (American Mineralogist Crystal Structure Database) of the IMA Database of Mineral Properties/ RRUFF Project, Univ. of Arizona, was preferred most of the time. Minor components in formulae have been left out to highlight the dominant chemical endmember that defines each species. Synthetic garnets Also known as rare-earth garnets. The crystallographic structure of garnets has been expanded from the prototype to include chemicals with the general formula A3B2(CO4)3. Besides silicon, a large number of elements have been put on the C site, including germanium, gallium, aluminum, vanadium and iron. Yttrium aluminium garnet (YAG), Y3Al2(AlO4)3, is used for synthetic gemstones. Due to its fairly high refractive index, YAG was used as a diamond simulant in the 1970s until the methods of producing the more advanced simulant cubic zirconia in commercial quantities were developed. When doped with neodymium (Nd3+), YAG may be used as the lasing medium in Nd:YAG lasers. When doped with erbium, it can be used as the lasing medium in Er:YAG lasers. When doped with gadolinium, it can be used as the lasing medium in Gd:YAG lasers. These doped YAG lasers are used in medical procedures including laser skin resurfacing, dentistry, and ophthalmology. Interesting magnetic properties arise when the appropriate elements are used. In yttrium iron garnet (YIG), Y3Fe2(FeO4)3, the five iron(III) ions occupy two octahedral and three tetrahedral sites, with the yttrium(III) ions coordinated by eight oxygen ions in an irregular cube. The iron ions in the two coordination sites exhibit different spins, resulting in magnetic behavior. YIG is a ferrimagnetic material having a Curie temperature of