Monday, September 22, 2008

Presa,dogo,cane Corso,boerboel

CLASSIFICATION OF MINERAL SCALE OF HARDNESS

Hardness Scale

The hardness of a mineral can be tested in several ways. Typically, compared to minerals scraped with an object of known hardness. For example, if a nail can scratch a glass , the nail is harder than that mineral. In 1820, Friedrich Mohs, an Austrian mineralogist, developed a relative hardness scale based on a test where the ore is scraped with an object. This is called the Mohs scale and a list of ten materials sorted according to their hardness , lowest to highest. Used as a reference on the hardness of a substance. It is based on the principle that a hard substance can scratch a softer substance, but it is not possible otherwise.

Mohs chose ten minerals those who attributed a degree of hardness on the scale starting with the talc, which was the number 1, and ending with diamond , which assigned the number 10.

Each mineral streak to having a number equal to or below it, and is lined by having a number equal to or greater than yours.

The hardest material is diamond (10) and the drive is less calcium (1).

covalent bonds usually hardest mineral form ionic bonds. The hardness of a mineral depends mainly on the type of link that exists between atoms.

The scale is not linear (the corundum is actually 4 times harder than quartz) and other newer methods offer more rigorous measures of hardness. Despite the lack of precision in the Moh's scale, it is still useful because it is simple, easy to remember and easy to prove. The steel of a knife (a common tool for geologists take the field), is located almost in the middle of its length, so it's easy distinguish the upper half of the bottom. For example, quartz and calcite can be very similar - both are clear, colorless, translucent and come in a variety of rocks. But a simple test can distinguish scraping, the blade or hammer scratch calcite but not quartz. Gypsum can also look a lot like calcite, but is so soft that it can be scratched with a fingernail.

The variations in hardness make minerals useful for different purposes. The softness of calcite makes it suitable for sculpture (marble is composed entirely of calcite ), while the hardness of diamond makes be used as an abrasive for polishing rocks.


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