A Purpose for Scratching Minerals

Did you know that some minerals you can scratch with your fingernail? Frederick Mohs invented the scale of 1 – 10 hardness.  All minerals are now fit into this scale of hardness.  Higher numbers scratch any number lower than that number.  For example, 7’s will scratch 6’s, but 6’s will not scratch 7’s.  Finding out the hardness of minerals is useful to help identify a mineral you have no idea what it is.

This is what he created:                                                                                            1   talc                                                                                                                        2   gypsum                                                                                                                3   calcite                                                                                                                   4    fluorite                                                                                                                  5    apatite                                                                                                                 6    orthoclase feldspar                                                                                             7    quartz                                                                                                                     8    topaz                                                                                                                   9    corundum                                                                                                         10  diamond

Any mineral with a number 1 or 2 hardness you can scratch with your fingernail.  The rest are harder.  In the Field guide to Rocks and Minerals from the National Audubon Society there is a full chart of each mineral’s hardness stated.

At many rock and mineral shops you can find a hardness testing kit which will give you tools to test how hard your mineral that you have is.  How it works is they give you all the minerals that are on the 1 to 10 hardness scale, except diamond.  You take your mineral and the number 9 hardness (H) mineral and try to scratch your mineral with the #9H mineral.  If it does scratch it means it is lower than #9. If it does not scratch it means it is a #9H mineral.  By making many tests you are enabled to find how hard your mineral is.

The next mineral that I will be studying is Beryl.  Beryl has a hardness of 7½ – 8, so Beryl can scratch Quartz.

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