Better question: Why should you aesthetically prefer a diamond to cheap glass?

You can make some plausible arguments against glass. It scratches more easily and doesn't shimmer as much. But synthetic sapphire is the same league and costs a lot less.

The modern-day aesthetic of diamonds is just that they are expensive. They're not distinguished by utility, quality, or appearance from cheaper products. The ultimate status symbol, but also obviously a bit of an issue...

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function_seven 5 days ago | parent | prev | next [-]

Diamonds sparkle a lot more brilliantly due to their high refractive index.

(Moissanite is even better, so it should be preferred over diamonds unless I’m overlooking some other difference in their attributes?)

But plain glass gems look comparatively bland when used as jewelry.

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mensetmanusman 5 days ago | parent [-]

Moissanite scratchers much easier.

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0cf8612b2e1e 5 days ago | parent | next [-]

I need a geologist to explain this one. Moissanite has a Mohs hardness of 9.5. I guess it is easier to scratch than a diamond, but the scratability should be indistinguishable between the two for all practical purposes.

	▲	jjmarr 5 days ago \| parent [-]
		Not a geologist but Mohs hardness is an ordinal scale so the distance between 10 and 9 isn't well-defined. The numbers are defined as being specific minerals. Diamond (10) is 4x as hard as corundum (9) which is 2x as hard as topaz (8). https://en.wikipedia.org/wiki/Mohs_scale#Reference_minerals

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cubefox 5 days ago | parent | prev | next [-]

Everything scratches easier than diamond. Moissanite is still very hard to scratch.

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function_seven 5 days ago | parent | prev [-]

Oh duh. I was so focused on optical qualities I didn’t even think about material ones.

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masfuerte 5 days ago | parent | prev | next [-]

Because they don't look the same. Not even a little bit.

Glass doesn't sparkle.

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throwmeaway222 5 days ago | parent [-]

If that's what makes real diamonds special, these shoes should we worth at least $100M

https://www.walmart.com/ip/Miluxas-Women-s-Glitter-Tennis-Sn...

	▲	kstrauser 5 days ago \| parent [-]
		OK, but there's a real difference. My wedding band has small diamonds in it, and occasionally I'll be sitting inside where the sun falls on my hand and casts a million pretty blue and white and red sparkles on the walls and ceiling of the room I'm in. Diamonds (and other gems) really are beautifula to look at in ways that glass just isn't. And manmade ones, sparklier still out of the forge of our own cleverness, are much nicer in my opinion.

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philjohn 5 days ago | parent | prev [-]

Because the refractive index of diamond is higher than that of glass, which makes it look prettier and "sparkle".