The infrared sp ectra of coesite, low-temperature tridymite, low-temperature cristobalitelow-~emperature quartz, vitreous silica, hexagonal Oe02, tetragonal Ge02, and vitreous germallla are reported from ~,OO O to 300 C~-l. Wherever possible an assignment of frequencies has been made on t he basls of the selectlOn rules for the crystal symmetry. Three characteris.tic gro up frequencies. near 1,lOq, 800, and 480 cm-1 are common to all the polymorphs of Sl02. Thes.e frequ~nCle.s respectlvely correspond to a str~tching mode i nvolving displacements assoclated prnnanly wlth the oxygen atoms, a stretclung mode involving displacements associated primarily . wi~h the. sil~co~ atoms, and a Si-O bending mode. The presence of these gro up frequencles III coeslte mdlcates that t he coordination of silicon in coesite is tetrahedral and that its high density is associated with the packinrr of tetrahedral units at an angle approximatiI?g 120 degrees.. The tetragonal and hexagon~l GC02 polymorphs show a marked dlfference III spectra due III part to the change from sixfold to fourfold coordination. The assignment of obscrved frequencies in hexagonal Ge02 is consistent with that made for low-temperature quartz if allowance is made for the heavier mass of t he Ge atom.

A synthetic fluorophlogopite mica (KMg3A1Si30 IO F 2), in which the (OR) ions that are normally found in normal micas were complet.ely replaced by fluorine, has been syn thesized. This material has essentially the same physical and electrical properties as natural phlogopite mica, except with somewhat lower flexibility. To grow large, usable sheets of mica. it is necessary to obtain pr"ferred crystal orientation, which depends primarily on controlled thermal gradients, batch composition, and rate of cooling. Platinum crucibles were found to be the best material for holding t he batch during the m elt. Data on the physical, electrical, thermal, and chemical properties of the synthetic mica are given.