One of the things that I had a hard time understanding was when I was told that glass was hard. In fact it is used to test if a diamond is a diamond, the hardest mineral. It confused me because glasses broke pretty easily. As a kid I broke many glasses and then was told that glass (hardness between 6-7 on MOH's scale) is harder than iron (hardness between 4-5 on the MOH's scale). I have never shattered iron. My problem was a misconception of what hardness is. Hardness is the resistance of a mineral to being scratched. It is not a test on when the material shatters. This websitehttp://www.oakton.edu/user/4/billtong/eas100lab/hardness.htm explains how to test hardness. You can look at this website to show that glass can be used to get a general idea of a minerals hardness like people do in movies or shows to test if a diamond is a diamond.
I looked up Cubic Zirconia's hardness since it must have a lower hardness than glass, but according to movies but according to this site
http://www.diffen.com/difference/Cubic_Zirconia_vs_Diamond. Cubic Zirconia's hardness is harder than glass, so should also scratch glass. I guess you cannot believe everything on tv and movies or you may buy fake diamonds!
Great post, it made me think also back to when I was in geology class doing those type of tests. Thanks for the great information and making it so that students can understand.
ReplyDeleteHardness testing by way of MOH's scale is one the primary tests for determining mineral type. Others include specific gravity, lustre, crystal type, color, magnetism, fracture, cleavage, and radioactive decay. Interestingly, metals use a scale known as the Rockwell Scale which tests for indentation under a load.
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