In September 2020, CDE Asia broke new grounds in quartz washing and installed a customized Combo plant (Combo Exo) to help its client achieve economies of cost and control over their quartz beneficiation and gradation process. Mineral Processing Systems for Beneficiating Low Grade OresĪdvanced Processing System for Industrial Sands His results aremarkedly at variance with those of Hurlbut (1946) for Brazilian quartz.Advanced Construction Sand Production Technology He also found that about half of those examined were right-handed and half were left-handed. Trommsdorf (1937) examined 4,483 crystals from Villa Cristallinanear Tres Capone, Brazil, and reported that 0.91 per cent were twinned according to the Brazil law. Heide (1928) tabulates data for twenty-eight twin halves of Japanese twins fromSaubach giving three with no twinning, fifteen twinned after the Dauphiné law,of which seven were left-handed and eight were right-handed, two after the Brazillaw and eight after the Dauphiné-Brazil law. No attempt will be made to cite all of thereferences some are noted in recent papers by Frondel, Parrish, Hurlbut, Gordonand others. Since 1940, becauseof the great war demand for quartz oscillator-plates in the radio industry,added impetus was given in the United States to the study of quartz and itstwinning by the work of Armstrong, Bond, Frondel, Gordon, Hurlbut, Parrish,Stoiber, Willard, and others. Among the manyworkers who prior to 1940 contributed to the study of quartz along these linesare Baumhauer, Bendrich, Bomer, Bond, Brauns, Des Cloiseaux, Drugman, Friedel,Gaudefroy, Gill, Goldschmidt, Heide, Hirschwald, Ichikawa, Kalb, Larsen, Leydolt,Martini, Meen, Meyer, Molengraaf, Mügge, Nacken, Niggli, Penfield, Rose, Sosman,Trommsdorf, Von Roth, Websky, Weiss, Wright, and Witteborg. Many of the references are concerned withdescriptions and study of quartz twins and twinning, the nature of the twinboundaries, quartz etch figures, vicinal faces, relations of form and twinningto temperature of formation, as well as geology and occurrence. There is a voluminous literature on quartz but it is beyond the scope of thispaper to review all of it. Wynn very kindly loaned his drawings of phantomcrystals from Brazil. Butler for discussions aboutthe phantom crystals. Sosman for constructivecriticism of the original manuscript, and to R. Wroe Wolfe kindly loaned histranslation of Friedel's Lecons de Cristallographie and Siemon Muller certainRussian translations. Thanks are extended to severalformer associates for gifts of certain crystals and for opportunities to discuss the problem. Honess for an introduction to theetch method and for encouragement in this study. The writer is indebted to the late Arthur P. Interestin this problem arose more from the geological implications than from the purelymineralogical aspects. A search through the literature disclosed manyarticles on twinning in quartz but there were few statistical data on thefrequency distribution of twin types and of right- and left-handed crystals.Further studies were made on additional crystals from these two localities andfrom four others in order to determine the frequency of twin types for eachlocality and the frequency of right- and left-handed quartz crystals. The crystals from the first locality showed considerably moretwinning than those from the second, although the unetched crystals gave noindication of any twinning. Honess,it became desirable to etch and study a few low-quartz crystals from twolocalities. Some years ago while engaged in etch-figure work with the late Dr. The local variations of twin ratios are thought to be areflection of geologicenvironment. It is suggested that crystalstwinned according to both the Dauphiné and Brazil laws should be called"Dauphiné-Brazil" twins rather than by the names that have beenpreviously applied. twinned quartz crystals are much morecommon than untwinned and that the frequencies of twin types and the ratiosbetween twin types vary from locality to locality. The frequency of twin types and the handedness were determined for 1,179crystals from six localities by the use of etch figures developed withhydrofluoric acid. THE FREQUENCY OF TWIN TYPES IN QUARTZ CRYSTALS 1
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