什么是莫氏硬度等级？

Mohs Hardness Scale.

Moh's hardness scale is a scale used to test minerals, rocks, or other materials for their hardness. Technically, it tests materials for their resistance to being scratched. It works by using ten different reference materials, with talc at the softest and diamond at the hardest. Aside from diamond, these minerals are relatively easy to obtain. The nice thing about the minerals being used for reference is that most samples of the minerals are the typical hardness.

The chart:

1: Talc
2: Gypsum
3: Calcite
4: Fluorite
5: Apatite (my favorite)
6: Orthoclase
7: Quartz
8: Topaz
9: Corundum
10: Diamond

Use these spellings for future questions by me.

Other important items in the field:

Fingernail: 2 to 2.5
Copper: 3
Nail: 4
Glass: 5.5
Knife blade: 5 to 6.5
Steel file: 6.5
Streak plate: 6.5 to 7

These materials are important because they will probably be on hand if you are mineral-hunting.

The Mohs Scale

The property of hardness has historically been measured according to the Mohs scale, which was created in 1824 by the Austrian mineralogist Friedrich Mohs. Mohs based his system for measuring and describing the hardness of a sample upon the definition of hardness as resistance to scratching. Mohs' method thus relies upon a scratch test in order to relate the hardness of a mineral specimen to a number from the Mohs scale.

In order to define his scale, Mohs assembled a set of common reference minerals of varying hardnesses and labled these in order of increasing hardness from 1 to 10. The reference minerals of the Mohs scale are as follows:

• Talc
• Gypsum
• Calcite
• Fluorite
• Apatite
• Orthoclase
• Quartz
• Topaz
• Corundum
• Diamond

Each reference mineral will scratch a test specimen with a Mohs hardness less than or equal to its own. Each reference mineral can be scratched by a specimen with a hardness equal to or greater than its own. If a reference mineral both scratches and can be scratched by a certain test specimen, then the specimen is assumed to possess a hardness equal to that of the reference mineral in question.

The set of reference minerals of the Mohs' scale can be supplemented by a few common household items. A fingernail has a Mohs hardness of $2 \frac12$; a copper penny $3$, window glass $5 \frac12$, and a knife blade approximately $6$.

The hardness of an unknown sample can be determined to within $\frac12$ increment by using the scratch test. Mineral hardnesses determined by the scratch test should never be given in decimal form, because the Mohs scale does not provide measurements of such precision.

The hardness of a mineral may vary with direction and crystallographic plane. This effect is usually small. However, species exist in which the variance in the hardness along different axes is notable. For example, the mineral kyanite (Al2OSiO4) typically forms elongated crystals. The Mohs hardness parallel to the length of a kyanite crystal is 5, whereas the Mohs hardness perpendicular to the length of such a crystal is 7. A second example is provided by the mineral halite, which is softer parallel to its cleavage planes than it is at a 45° angle to the cleavage planes.