Hydroxylherderite

Hydroxylherderite was named in 1894 for its compositional relationship to herderite in honor of Siegmund August Wolfgang von Herder of Freiberg, Saxony, Germany. It is a calcium-beryllium phosphate that is the OH end-member of the herderite-hydroxylherdite series. Predominantly found in granite pegmatites as subhedral to euhedral crystal sections of varying size, and is not uncommon as well-formed crystals in miarolitic cavities in granite pegmatite as stout, prismatic [001], [100] or tabular [001], pseudo-orthorhombic or pseudohexagonal crystals, and botryoidal aggregates with a radial fibrous structure. Hydroxlherderite forms transparent, translucent, to nearly opaque, colorless, gray, brown, pale yellow, greenish white, light blue, or purple crystals with a vitreous to resinous luster. It is commonly twinned {001} or {100} as fishtail contact twins. Associated minerals include: topaz, microcline, quartz, albite, lepidolite, elbaite, muscovite, and beryllonite. Notable localities in the U.S. include: the Blue Chihuahua mine, Riverside Co.; the Himalaya and Green Cloud mines, San Diego Co., California; the Bennett Quarry, Waisanen Quarry, Dunton Gem and Newry mines, Oxford Co.; and Berry Quarry, Androscoggin Co., Maine. Exceptional crystals are found in Minas Gerais state, Brazil at the Xanda mine, Virgem da Lapa; Lavra do Enio, Galileia; and the Golconda mine, Governador Valadares. In recent years, good crystals have originated from the Skardu district, Baltistan, Northern Areas, Pakistan, as well as the Darra-i-Pech Pegmatite Field, Nangarhar, Province, and at Paprok, Nuristan Province, Afghanistan.

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