Science!

Eeyore said

My grandfather had part of his lung removed because of it and died of lung cancer years later.

Diamonds would probably be similar to fiberglass in the lungs. Safer than asbestos. Probably.

Click to expand...

IDK, they are finding the silica dust from coal mining much worse than coal and volcanic ash basically turns into cement inside u.

I'd imagine tiny shards of jagged angular hard as diamond bits slicing air sacs could be quite devastating in a very short time if the count was sufficient enough.