Hrm. This is a very atypical post by the President. Even though this article is recent, the news is quite old. Diamonds are just carbon atoms in a very specific pattern (tetrahedrons with unusually strong covalent bonds). Synthetic diamonds have been created with increasing precision for many years now.

The word "diamond" does not appear in a single Q drop.

But ultimately, a diamond is just a stone. While the word "keystone" is a very familiar term for those acquainted with Q, the word "stone" is used once by itself in a somewhat unusual drop (2661 https://qagg.news/?read=2661):

https://twitter.com/maggienyt/status/1009982937952079873?lang=en
https://twitter.com/maggienyt/status/1065100343846031362?lang=en

A stone sits idle while the world around it evolves. Evolution, depending on the stage, can be deadly.

https://twitter.com/maggieNYT/status/1081974511598211072

We can talk through code or we can act through transparency. The choice is yours. However, the clock is ticking, and, at a select point in time, that option will be expired. Regular service appointments should be made in order to maintain functionality. Q

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Some very unusual tweets there by Maggie Haberman. There's one other Q drop I'll point out where "stone" is broken out from "Keystone" (Q drop 271 https://qagg.news/?read=271)

Military Intelligence, No Such Agency = key
POTUS and Patriots = stone

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I do not know what to make of this post on TS by President Trump, but I agree with the OP that it appears to be comms. But I'm at a loss to explain the meaning.