Showing papers in "American Mineralogist in 1950"

Differential thermal analysis curves of carbonate minerals

Abstract: Fifty-one differential thermal analysis curves are presented and interpreted. These curves are of forty-eight carbonate minerals, one artificial carbonate, one oxide mineral, and one artificial oxide.

Three new polymorphs of zinc sulfide

Abstract: Three new polymorphs of zinc sulfide are described. All are related structurally to wurtzite but difier in that they represent stacking sequences of hexagonal closest-packing of higher periodicity than that of the basic wurtzite structure. The latter structure may be designated 2H in the nomenclature of Ramsdell (1947). The new polymorphs correspond to 4H, 6H and 15R, and are isotypic with the corresponding polymorphs of silicon carbide. A tabulation of the crystallographic properties follows.

An attempt to arrange silicates in the order of reaction energies at relatively low temperatures

Abstract: There have been attempts from time to time to arrange minerals, especially the silicates, in some order which would correspond to their sequence of formation, or their order of stability, or perhaps their order of energy of reaction under a given set of conditions. Bowen's Reaction Series, familiar to all of us, is an example. Many of us who are here today were inspired by the address of our past-president, Professor M. J. Buerger (1948), two years ago on the stability relations of minerals and by his recent contribution (1948) on silica-bridging in structures. Another very creditable attempt was made by H. W. Fairbairn (1943) in his paper on packing indexes of ions. His figures, while unquestionably important, did not lead to any mineral series of either formation or stability though probably were included in both and formed a part of each of them. It should be possible, however, to arrange the minerals in some kind of an order which would tell us something of their reaction energies under a given set of conditions, let us say for illustration, weathering or at any rate, conditions under which water plays an important role at not a very high temperature, and proton transfer becomes important,.