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Mohs hardness, rough measure of the resistance of a smooth surface to scratching or abrasion, expressed in terms of a scale devised (1812) by the German mineralogist Friedrich Mohs. The Mohs hardness of a mineral is determined by observing whether its surface is scratched by a substance of known or defined hardness.
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To give numerical values to this physical property, minerals are ranked along the Mohs scale, which is composed of 10 minerals that have been given arbitrary hardness values. The minerals contained in the scale are shown in the Table; also shown are other materials that approximate the hardness of some of the minerals. As is indicated by the ranking in the scale, if a mineral is scratched by orthoclase but not by apatite, its Mohs hardness is between 5 and 6. In the determination procedure it is necessary to be certain that a scratch is actually made and not just a “chalk” mark that will rub off. If the species being tested is fine-grained, friable, or pulverulent, the test may only loosen grains without testing individual mineral surfaces; thus, certain textures or aggregate forms may hinder or prevent a true hardness determination. For this reason the Mohs test, while greatly facilitating the identification of minerals in the field, is not suitable for accurately gauging the hardness of industrial materials such as steel or ceramics. (For these materials a more precise measure is to be found in the Vickers hardness or Knoop hardness) Another disadvantage of the Mohs scale is that it is not linear; that is, each increment of one in the scale does not indicate a proportional increase in hardness. For instance, the progression from calcite to fluorite (from 3 to 4 on the Mohs scale) reflects an increase in hardness of approximately 25 percent; the progression from corundum to diamond, on the other hand (9 to 10 on the Mohs scale), reflects a hardness increase of more than 300 percent.
Aerial view of Great Zimbabwe's Great Enclosure and adjacent ruins, looking ... from trading centers along the Zambezi River and from Central African kingdoms.
Dionisio “Dennis” Chávez was the first Hispanic Senator in the USA and to be born in the state of New Mexico.
During his term as senator the State of New Mexico faced a great epidemic of influenza. The state fined citizens for sneezing and spitting. In a few months there were more than 5,000 deaths due to this cause. In addition many men from New Mexico participated in the First World War and were generally affected in all families. The citizens wanted to return to normal.
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Since you probily forgot to put the statements in the question can you put them in the ch-at so i can answer i there.
They visited China's Tang court here they spoke Chinese and dressed similarly to Chinese
