Mohs Hardness Scale

It's common sense that some objects are harder than others. We refer to this characteristic as hardness. (clears throat) But what exactly is hardness? Let me tell you, it's the ability of a material to resist being damaged, scratched, or marred in any way. There's even a way to measure it. It's the Mohs scale of hardness. A German scientist, um, a mineralogist named Friedrich Mohs came up with the scale in 1812. Here's how he made it. Mohs took 10 different minerals. Then he rated them from 1 to 10 based on their ability to withstand damage and to damage other materials. TELC received a rating of 1. It's soft, it's easily scratched, and can hardly damage anything. Diamond received a rating of 10. It's the hardest natural substance known to man. The other objects on the scale that number from 2 to 9 are gypsum, calcite, fluoride, appetite, felt spar, quartz, topaz, and corundum. I see worried looks on your faces. Don't worry about writing them down. They're listed on page 234 of your text. Take a look. Now, what about the hardness of other objects? Hmm, it depends on which of the ten minerals can scratch them. For instance, your fingernails get a rating of 2.5 on the Moh scale, so talc and gypsum can't scratch them, but calcite can. What are some others? Let's see. Iron is rated between 4 and 5. Glass is between 6 and 7. And steel is close to 8. Type.