I'm not answering the question you asked
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You can ride your frame on gravel without issue. The cinders or even coarse gravel won't have enough energy to compromise your frame. BUT, continued impact from gravel can easily chip paint. I can imagine a carbon frame with no mitigation for kicked up gravel having the paint wear away after years of use exclusively on decomposed granite trails.
Once in a while won't do too much damage, but you'll be able to see small chips and nicks after the first few times.