Really really really really really hard minerals
June 23, 2018 12:16 PM   Subscribe

Ok, so this is the first Metafilter question coming from my daughter, who is six. According to DK's My Book of Rocks and Minerals, "Diamond can be scratched by two known rare minerals". The book does not elaborate. What are these two minerals? Google is confusing me today.
posted by selfnoise to Science & Nature (8 answers total) 4 users marked this as a favorite
Best answer: This article says wurtzite boron nitride and lonsdaleite.
posted by dilaudid at 12:28 PM on June 23, 2018 [1 favorite]

Best answer: According to the Wikipedia entry on the Mohs scale of mineral hardness, two substances that can scratch diamonds (and thus have a Mohs number of 11 or higher, compared to diamond's 10) are aggregated diamond nanorods ("hyperdiamonds") and rhenium diboride.
posted by Faint of Butt at 12:30 PM on June 23, 2018 [2 favorites]

Best answer: Russian super diamonds contain some lonsdaleite.
posted by hortense at 2:15 PM on June 23, 2018

Response by poster: Thanks all. She has now moved on to "what if the Moon was made of diamond; would an asteroid bounce off?" Oy vey.
posted by selfnoise at 7:31 PM on June 23, 2018 [12 favorites]

Q2: no, scratching hardness does not equal brittleness or cleavag habits or potential. Diamonds can be rather brittle and though metal.wil not scratch a diamond, you can take a metal hammer and smash a diamond. Which is to say, an asteroid would not bounce off, it would fracture the diamond moon and probably throw up a lot of little diamond shards and dust from the impact.
posted by rmless at 7:54 PM on June 23, 2018 [5 favorites]

A moon made of diamond might seem far fetched, but no!

Astronomers think they've found a star the size of the Earth which is essentially one big diamond.
posted by jamjam at 8:34 PM on June 23, 2018 [7 favorites]

I'd tell her that if the moon were made of diamond and was the right shape then the asteroid might shatter but then we'd know the moon was made of diamond and fight wars over it and there'd be no moon at all.

Early education is so important.
posted by Mr. Yuck at 1:35 AM on June 24, 2018 [6 favorites]

Q2 can be easily answered by showing her videos of workers cutting/splitting raw diamonds.
posted by Thorzdad at 6:11 AM on June 24, 2018

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