Hardness of minerals

To determine the hardness of minerals, the Mohs scale, proposed in 1811 by Friedrich Moos, is widely used in jewelry and gemology. This scale is a list of ten minerals with numbers from 1 up to 10, which serve to determine the relative hardness of minerals:

To determine the hardness of minerals, the Mohs scale, proposed in 1811 by Friedrich Moos, is widely used in jewelry and gemology

Thus, the talc mineral has a hardness of 1, apatite - 5, and diamond - 10. Determine the hardness of all other minerals by scratching - if there is a trace on the mineral, its hardness is lower than that of the mineral that was scraped, and if not - then higher. Thus, the Mohs scale informs only of the relative hardness of the minerals. For example, corundum (9) is 2 times harder than topaz (8), but it is almost 4 times less solid than diamond (10). Saying that the stone has a hardness of 7, we mean that it does not scratch quartz, and quartz does not scratch it. The number on the hardness scale indicates only the order in the hardness distribution, but does not have any quantitative value. This is important to take into account, as it is often erroneous here. One can not, for example, consider that diamond (10) is twice as hard as apatite (5) or that the hardness of topaz and spinel (8) is 80% of diamond hardness. In fact, the interval between diamond and corundum is much greater than between corundum and talc - the softest of minerals. Intermediate degrees of hardness are expressed in the form of fractions. Thus, the number 8 1/2, referring to chrysoberyl, means that it scratches topaz in approximately the same way as it is scratched by corundum. Also, the hardness of minerals is distinguished by indentation and grinding. Precise determination of the hardness of minerals is made by special instruments - sclerometers and hardness meters.

In addition to the Mohs scale, there are other methods to determine the hardness of minerals, but different hardness scales can not be uniquely correlated with each other. Practice has taken several more accurate systems for measuring the hardness of materials, none of which covers the entire spectrum of the Mohs scale.

  1. Talc.
  2. Gypsum
  3. Calcite
  4. Fluorite.
  5. Apatite
  6. Orthoclase.
  7. Quartz
  8. Topaz
  9. Corundum
  10. Diamond

To determine the hardness at home, reference minerals can be replaced by other things. For example, the softest pencil has a hardness of 1, the finger nail - 2-2,5, a copper coin - 3, glass - 5, file - 7.

While establishing the hardness of minerals helps little in determining gemstone, this very characteristic is very important for a stone in ornaments, since it depends on the hardness of the longevity of its polishing and gloss. The usual dust is basically the smallest quartz particles, so the hardness of the gemstone must be at least 7. Glass pastes have a hardness only slightly above 5, and therefore, as experience shows, their polishing can withstand only a few weeks of constant wear, not to mention the devastating action on their surface of harmful impurities in the air.