Mohs' scale of mineral hardness was created by the German mineralogist Friedrich Mohs in 1822 to measure the relative hardness or scratch resistance of various minerals. He based it on ten readily available minerals. As it is an ordinal scale, you have to compare two minerals to decide which is harder. The scale is neither linear nor logarithmic. For example, corundum is twice as hard as topaz, but diamond is almost four times as hard as corundum.
The hardness of a material is measured against the scale by finding the hardest material that that the given material can scratch, or the softest material that can scratch the given material.
To give some examples from everyday life, a fingernail has a hardness of 2; a copper penny, about 3; a knife blade, 5; window glass, 5.5; and a steel file, 6.5.
Here are the Mohs scale ratings for 144 types of gemstones:
Excellent. Items were gorgeous and exactly as pictured. Ordered on Monday, rec'd. Thursday AM !! I liked the website and the details of the items. It was an easy, fast and clean transaction. Admitting here that I have purchased from GemsTV and found that some gems ordered were less than advertised. Now I am happy that I can see an exact picture of the item I am to receive.
I have ordered several gems from Gemselect and I am very pleased with both the price and the quality. The gems are perfect in every way. I took one gem topaz london blue and the server couldn't believe the color, and the cut of the gem. He thought I paid a lot of money for the gem. I didn't say how much I paid, but he was very impressed. I felt proud that I was holding in my hand a very special gem. It made me realize just how much profit jewellery stores are making. Gemselect gems are...
Very fast shipping from Thailand to Conus. Gems were as advertised. Compared to some other the other gem dealers on the web I've dealt with Gem Select are very professional. Will definitely do more business with this proprietor.