I am wondering too because I have lots of alluvial glassy samples
of 1/2 mm or less from my prospecting in BC. Could some of them be
diamonds? How would I know?
One way is to check each individual stone with a diamond tester.
Then the other way is to put them all in the tumbler & hope for the
best. If there’s both diamonds & softer material, the softer
material may be partially eroded away.