 | Good Roads Institute, Chapel Hill, N.C. - 1897 - 1172 Seiten
...they were successfully worked, but as soon as the hard rock was encountered the mine had to shut down. There are three names in constant use to designate...varieties of corundum: 1. Sapphire, which includes all of those corundums that are transparent to semi-transparent, of whatever color ; 2. Corundum, including... | |
 | United States. Bureau of Mines - 1902 - 1002 Seiten
...garnet since 1894. CORUNDUM AND EMKRY. A distinction is often made between corundum and emery, many not recognizing emery as a variety of corundum. There...mechanical admixture of corundum and magnetite or hematite. It is these last two varieties that are used in the arts for abrasive purposes, ornery being used in... | |
 | United States. Bureau of Mines - 1902 - 1012 Seiten
...often made between corundum and emery, many not recognizing emery as a variety of corundum. There arc three names in constant use to designate the varieties...mechanical admixture of corundum and magnetite or hematite. It is these last two varieties that are used in the arts for abrasive purposes, emery being used in... | |
 | North Carolina. Department of Conservation and Development - 1902 - 112 Seiten
...they were successfully worked, but as soon as the hard rock was encountered the mine had to shut down. There are three names in constant use to designate...varieties of corundum: 1. Sapphire, which includes all of those corundums that are transparent to semi-transparent. of whatever color; 2. Corundum, including... | |
 | North Carolina. Department of Agriculture - 1923 - 406 Seiten
...transparent to semi-transparent, of whatever color. 2. Corundum, including the translucent to the opaque, of all colors. 3. Emery, which is a mechanical admixture...or hematite. The last two varieties are those used in the arts for abrasive purposes; the eme'ry being used in very much larger quantities than the corundum.... | |
 | United States. Bureau of Mines - 1902 - 1012 Seiten
...gnrnfl since 1S94. CORUNDUM AND EMERY. A distinction is often made between corundum and emery, many not recognizing emery as a variety of corundum. There...varieties of corundum: (1) Sapphire, which includes nil corundums of whatever color that are transparent to scmitransparent; (2) Corundum, including the... | |
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A distinction is often made between corundum and emery, many not recognizing emery as a variety of corundum. There are three names in constant use to designate the varieties of corundum: (1) Sapphire, which includes all corundums of whatever color that... 