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It is known [1][2][3][4][5][6] that in the production of dinas articles from quartz, or with additions of it, it is necessary to use finely dispersed bodies, to incorporate the lime--iron bond, and to observe the appropriate firing cycle. Although the main trends in the production of dinas from vein quartz are well known, with the use of actual varieties it is necessary to study the quartz rock and to tighten up the technical parameters of production.In recent years vein quartz has been found in the crystalline~quartzites of the Karaulsk Mountains used at the Pervouralsk dinas factory, in the form of veins and small sections of veins.Using such quartzites causes a sharp rise in the loss due to product cracking.The present article describes the results of a study of the suitability of Pervouralsk quartzites with impurities of vein quartz for the production of dinas.A sample of quartzite (2-3 tons) selected at the mine was distinguished by the color of the lumps.The predominant part of the sample was light gray, and the rest white, frequently of a laminated structure; small amounts of gray-white and dark-gray pieces were encountered. The surfaces of all four varieties of the sample were coated with deposits, brown, light brown, light-yellow, and white in color. We studied the light-gray and pale varieties of the sample (Table i).Petrographic studies showed that the specimens light-gray in color are composed of transparent colorless grains of quartz of irregular and elongated form, the edges of the grains were jagged and in close contact with each other.There was no cement. The grain sizes vary from 3.4 xl.7 to 0.43-0.34 mm; grains measuring 1.5-096 and 0.17-0.09 mm predominate.Thedistribution of the coarse and fine grains was irregular. Sometimes the grains of quartz contain inclusions of bubbles and also very fine needles,~of rutile, grains of zircon, and idiomorphic crystals of pyrites.In the microcracks could be seen accumulations of finely dispersed pyrites and products of its oxidation, and also inclusions of muscovite. The yellow deposit on the surface of the rock consists of iron and silicon hydroxides.The white variety consists of large grains of quartz of irregular and elongated form measuring from 4 to 18 mm. The grains of quartz are colorless, containing large amounts of fine gas bubbles.The contact between the grains aredense and tortuous. Cement is absent. The impurity consists of small amounts of iron hydroxide.The composition of the yellowgray deposit on the surface of the specimen is the same as in the light-gray specimen.Thus, the vein quartz differs from the quartzite by the coarser grains of quartz and the larger amount of gas bubbles in them.In order to study the degree of embrittlement of the quartzites during firing, the lumps of rock after determination of porosity were fired for 1 h at 1450~The results are shown in Table 2. From the degree of decomposition of the quartzite and quartz they were classified as very slowly transformable materials.The compressive strength of these materials is, r...

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