What does it mean to be “hard as a rock”? That depends entirely on the rock. To measure the hardness of a metal or mineral, we employ the Mohs scale of hardness. The Mohs scale runs from 1 through 10, with 1 being the easiest material to scratch and 10 being the most difficult. A mineral can only scratch another mineral of lesser value on the scale. For instance, quartz, which has a Mohs value of 7, can scratch turquoise, which has a value of about 6. However, quartz cannot scratch neither topaz at 8 nor diamond, the hardest mineral, at 10.
This is more than just a fun trick. You can find numerous scientific and industrial applications of the Mohs hardness kit—the collection of labeled minerals we use to scratch unknown quantities, determine Mohs values, and learn just what it is we’re working with. Some of these applications may be useful in your industry.
Geology
Perhaps the most common use of the Mohs hardness kit is in geology. When a well-trained eye or a visual field guide are insufficient in putting a name to an unidentifiable rock, the Mohs kit comes into play. Having a kit on hand to scratch minerals is an easy way to identify substances in the field without having to take them back to the laboratory for further testing.
Recycling
A Mohs kit also comes in handy when recyclers need to decipher a mysterious piece of metal. By applying test pieces to the subject, adept scrappers can identify scrap metal without sparks or chemicals and gauge its value accordingly. Some of the metals for which scrapyards are most on the lookout, such as tin, zinc, and lead, have Mohs values below 3, making them easy to scratch and subsequently easy to identify.
Manufacturing
There may be an important application of the Mohs hardness kit in your hand at this very moment. Your smartphone uses not just any glass, but specially treated glass that’s resistant to scratching and fracturing (though some clumsy or unfortunate users may have overcome this resistance). To perform quality control on smartphone screens, manufacturers will test tempered glass with a Mohs kit to make sure it can withstand scratches from substances up to a 6 on the Mohs scale. The Mohs kit also comes into use for industrial cutting tools to determine exactly what they can cut—a setting that’s quite different from a geological dig.
