Minerals Hardness Determination
Minerals are substances that are composed of a combination of elements that occur naturally. Their hardness is one of the most important characteristics of a mineral and it is what allows them to form durable materials such as rocks and tools. Knowing the hardness of a specific mineral can be extremely useful for identifying, classifying, and collecting certain minerals.
The most common way to measure the hardness of a mineral is using the Mohs Scale of hardness. It is a relative scale which means that the hardness of one mineral can be determined by testing its scratch resistance relative to the other minerals on the scale. It is based on 10 standard minerals which are arranged in order of increasing hardness. These minerals include talc (1), gypsum (2), calcite (3), fluorite (4) apatite (5), orthoclase (6), quartz (7), topaz (8), corundum (9), and diamond (10). The scale can be used to compare the hardness of any other mineral relative to these minerals.
The procedure for determining the hardness of a mineral on the Mohs scale involves assessing the scratches a mineral produces on other minerals. In this method, a mineral with a lower hardness on the Mohs scale (such as the talc) is used as the scratch tool and is rubbed against the surface of the mineral to be tested. If the mineral produces a scratch it is considered to be of a higher hardness than the mineral used as the scratch tool. This process is repeated with a mineral of higher hardness on the Mohs scale and the process is continued until a mineral is found that does not produce a scratch. The hardness of the mineral that does not produce a scratch is taken to be the hardness of the mineral under test.
The hardness of a mineral can also be determined by testing its ability to be etched. In this method, the mineral is placed under a microscope and then acid is applied to the surface. If the acid produces an effect on the surface (such as changes in color or texture) then the mineral has a lower hardness than the acid used, otherwise the mineral has a higher hardness than the acid used.
The hardness of a mineral can be a very helpful tool in identifying, classifying, and collecting certain minerals. Knowing the hardness of a mineral can also be used to determine how durable the mineral is and how best it might be used in various applications. It is important to remember, however, that hardness is only one of the many characteristics that are used to identify, classify, and collect minerals.
