mineral collectors. Optical properties Ajoite is translucent and bluish green in color, with a pale greenish white streak and a vitreous luster. The optical class is biaxial (+) with refractive indices Nx = 1.550, Ny = 1.583 and Nz = 1.641. These values are similar to the refractive index of ordinary window glass, at 1.5. In white light the mineral is distinctly pleochroic, being very light bluish green along the X direction and brilliant bluish green along the Y and Z directions. Physical properties The cleavage is perfect parallel to the plane containing the a and c axes, and the hardness is 3.5, between that of calcite and fluorite. It is a little denser than quartz, with specific gravity 2.96. Ajoite is readily decomposed by hydrochloric acid, HCl, and by nitric acid, HNO3, but it does not react with ammonium hydroxide, NH4OH. It has been reported as having barely detectable radioactivity. Environment Ajoite is a secondary mineral that forms from the oxidation of other secondary copper minerals in copper-rich base metal deposits in massive fracture coatings, in vein fillings, and in vugs. It may form from shattuckite and also it may be replaced by shattuckite. At the type locality it is associated with shattuckite, conichalcite, quartz, muscovite and pyrite. Occurrence Ajoite is named after its type locality, the New Cornelia Mine in the Ajo District of Pima County, Arizona. Type material is conserved at the National Museum of Natural History, Washington DC, USA, reference number 113220. Other localities include Wickenburg and Maricopa County in Arizona, within the United States, and the Messina (Musina) District in South Africa. Quartz specimens from the defunct Messina Mines on the border between Zimbabwe and South Africa are well known for their inclusions of blue copper silicate minerals such as shattuckite, papagoite and ajoite, but ajoite from American localities does not occur like this. References External links Ajoite photos JMol Phyllosilicates Copper(II) minerals Pima County, Arizona Triclinic minerals Minerals in space group 2