Ajoite is a hydrated sodium potassium copper aluminium silicate hydroxide mineral. Ajoite has the chemical formula (Na,K)Cu7AlSi9O24(OH)6·3H2O, and minor Mn, Fe and Ca are usually also present in the structure. Ajoite is used as a minor ore of copper. Discovery In August 1941 Harry Berman of Harvard University was collecting at Ajo, in Pima County, Arizona, USA. He found specimens of dark blue shattuckite, together with a bluish green mineral which he suspected was a new species. Berman and W T Schaller had planned to collaborate on the investigation of this mineral, together with other known copper silicate minerals, but Berman died in a plane crash in 1944, aged 42, before this study was done. It was not until 1958 that Schaller, together with Angelina Vlisidis (both of the US Geological Survey) studied the greenish mineral and determined that it was indeed a new species. They named it "ajoite" (pronounced ah-hoe-ite) after the place where it had been found. Twenty three years later, in 1981, George Chao from Carleton University in Ottawa, Canada, studied the mineral again, and showed that ajoite was triclinic, and not monoclinic as had been thought previously. His studies also resulted in a re-definition of the chemical formula. Crystal structure The 1981 investigations of ajoite were done on a sample from the New Cornelia Mine, Ajo, with tiny crystals averaging 0.01×0.1×0.4 mm. The mineral was shown to belong to the triclinic system, but it was not clear whether the crystal class was 1 or . The triclinic class 1 has the lowest possible symmetry with no symmetry elements at all, and has just a centre of symmetry, but no axes of symmetry or mirror planes. The space group is either P1 or P. The unit cell parameters are: a = 13.637 Å, b = 14.507 Å, c = 13.620 Å, α = 107.16°, β = 105.45° and γ = 110.57°. Ajoite occurs as sprays of bladed prismatic crystals, commonly fibrous, elongated along the c crystal axis and flattened sideways. The dominant form is , parallel to the plane containing the a and c axes. The forms , cutting both the a and b axes, and , parallel to the plane containing the b and c axes, are much less prominent but are always present. The termination on c may be either or or both. Ajoite is frequently found as inclusions in quartz, much sought after by