Abstract
The near end-member minerals fluorphlogopite (XF = 0.96) and fluortremolite (XF = 0.82) have been found in Grenville marbles near Balmat, New York. These micas and amphiboles, like other fluorine-rich minerals reported in the literature, are extremely low in iron. The substitution of F for OH is partly responsible for stabilizing these minerals in the granulite facies marbles of the Adirondacks. Fluorine-rich amphiboles and micas are more common than generally recognized. A literature review shows that many amphiboles and micas have more than fifty percent of the interlayer site occupied by fluorine. This degree of solid solution qualifies these phases as independent minerals, but they are not currently recognized by the I.M.A. We propose that fluorbiotite, fluorphlogopite, fluoractinolite, fluorarfvedsonite, fluoredenite, fluorhastingsite, fluorpargasite, fluorrichterite, fluorriebeckite, fluortremolite, fluoredenitic hornblende, fluorhastingsitic hornblende, fluorpargasitic hornblende, fluortremolitic hornblende, fluorferro-edenite, and fluormagnesio-arfved-sonite be formally applied as mineral names for these phases. Identification of the mineralogically and petrologically important solid solution of fluorine for hydroxyl is currently obscured by use of names that imply hydroxyl end-members.
