Episode 156: Mohs Scale of Hardness

A: This is KSU student podcast. My name is Kotaro and this is Koji.

B: Today, we have an interesting topic. Kotaro, do you know what material is the hardest in the world?

A: Of course! It’s Diamond!

B: Ah, I suspected you’d say so! First of all, can you explain what hardness is?

A: …A scale of durability against shock?

B: No. Hardness, Mohs scale of hardness, says that “Hardness is a degree of durability against scratches.”, so it’s not a scale of toughness.

A: You mean that diamond is the most difficult material to scratch, but it doesn’t mean that diamond is the toughest material. However, I cannot imagine a material that has high hardness, but weak to shock.

B: OK. For example, you can break glass by your hand, but when you scratch your hand with glass, you get wounded.

A: That makes sense! By the way, what mineral is tougher than diamond? Famous one, please.

B: Hmm…In famous minerals, jade or ruby or… Others are not famous.

A: Then, what is the toughest material in the world?

B: It’s carbonado, known as black diamond. It consists for minute particle of diamond. Jade and ruby have 80% hardness of carbonado, and diamond has 75%. It’s expensive because of its rarity, but cheaper than diamond, because usually we don’t use it for accessories.

A: I see. In the end, the hardest material is black diamond. It consists of diamond, doesn’t it?

B: Actually, no.

A: Then, what is that?

B: It’s carbyne. It consists of carbon, the as same as diamond, but the carbon atoms are connected like a chain.

A: How hard is it?

B: About 3 times as hard as diamond.

A: Wow, these facts are very interesting to me! Can I tell you one thing about diamond?

B: Of course!

A: We wear white gloves and use tweezers when we touch diamond, did you know that?

B: Yeah. I’ve seen it on TV shopping!

A: Then, do you know why they do so?

B: I don’t know. Why?

A: Diamond absorb oil easily, so we wear groves and use tweezers to prevent making them dirty with our hands.

B: That’s interesting! Diamonds have many characteristics.  

A: I think that’s all for today. Thanks for listening to KSU Student Podcast. We hope you have learned something new.