# PTE HCS #7: Mineral Hardness Classification...

Highlight Correct Summary #7 - Level 2 - Feeds Reading + Listening

> You will hear a recording. Choose the paragraph that best summarizes it.

- The hardest mineral is determined by Mohs Scale of Hardness. Diamonds are close to glass in hardness, and Gypsum is known as the softest substance on Mohs.
- Mohs Scale of Hardness is created to rate minerals. Hardness refers to a material's ability to scratch other objects and different materials are received different ranks on this scale.
- Friedrich Mohs was the first person to realize how hard diamonds are. The professor tells the students to look in their textbooks so that they can learn about the hardness of them.

## Answer

Mohs Scale of Hardness is created to rate minerals. Hardness refers to a material's ability to scratch other objects and different materials are received different ranks on this scale.

## Explanation

The correct option accurately captures the essence of the lecture by defining the purpose of the scale and the concept of hardness as a relative measurement.

## Hints

- Focus on the overall purpose of the scale rather than specific mineral names.
- Look for the option that explains what the scale measures and why it exists.

## Transcript

It's common sense that some objects are harder than others. We refer to this characteristic as hardness. 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. 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. Talc 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, fluorite, apatite, feldspar, 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 Mohs 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.

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