|
Post by joe on Nov 14, 2005 19:10:58 GMT -5
Every mineral has a property called "hardness". Some minerals (diamond) are harder than others (talc). The harder minerals take the best shine. A quick method for determining the hardness of a mineral is the scratch test. I'll try to describe it. Click the link and look at the MOH chart at: www.amfed.org/t_mohs.htmEach of the materials at the bottom of the page can be used to try to scratch rock. Also rocks of a known hardness such as quartz (MOH 7) can be used to scratch unknown rock. Try the copper coin first. Give the rock a good HARD scratch. Look at the scratch with a magnifier. (I like 10x) You will see that the copper probably did NOT scratch the rock and that the rock has a copper streak on it where the copper wore off. The copper was scratched, not the rock. Now try scratching the rock with a knife blade. Do NOT use a knife you like as this will ruin the blade. Pick out a sacrificial cheap knife and use it. Do not use a Swiss army knife. The steel on those things is harder than a cheap knife and will throw off the test results. If you can successfully scratch the rock than the rock is 5 to 6 on the MOH scale. Maybe a feldspar. Get a quartz crystal. Use it to perform the test. Quartz will scratch other quartz. This is not the most exact test in the world but with a few items to scratch with you can get a general idea of the hardness of a rock. This may not be too clear but I hope it helps.
|
|