Do certain gemstones hold stormlight more effectively?

[Cyanic he/him]

If it was discussed in the books, I probably missed it. Anyway, we know that broams hold more stormlight than chips, but I'm asking whether certain gemstones can hold more stormlight than others (i.e. do emeralds hold more than diamonds?)

[Calderis he/him]

Not that we're told. The only things that we know effect how long a gemstone retains light are size (due to greater amount) and the cut. 

The better the cut a gem is, the longer it will retain its Stormlight. 

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Alteroden

With Stormlight, the better the gem is cut, the less Stormlight it leaks, and the longer it holds its charge. If a gem was perfectly cut, on a molecular scale, would it leak Stormlight at all?

Brandon Sanderson

In a theoretical flawless gem, then no it would not.

Alteroden

Would it actually give off light?

Brandon Sanderson

[...] Theoretically no it would not, but it's not what you're thinking...

Alteroden

No no no, that’s not what I’m thinking, I figured that’s something totally different.

Brandon Sanderson

Well, actually, it probably would still give off light, because it's drawing out of the Spiritual Realm. So I’d say it still lights, but it doesn't leak. The leaking is not where the illumination is coming from. The illumination is coming from a direct... It's basically a light bulb screwed into the Spiritual Realm

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Questioner

What is the gem cut that holds the most Stormlight, and does it vary from gem to gem?

Brandon Sanderson

It does vary from gem to gem, and... I've got this written down somewhere... I am going RAFO, because it's more of a "go to my notes and find out."

That "varies from gem to gem," by my interpretation, also means that the quality of the gem itself is going to have an effect. So inclusions and impurities in the gemstones will also have an effect. 

[Cyanic he/him]

Makes sense. Thank you