I have a couple dozen such diamonds I bought in India. In the main
diamond-cutting centre of Surat they specialize in these tiny grains
of dust… and they do them manually.
Unfortunately it’s mostly kids that do the cutting as they’re the
ones with the small enough hands and keen eyes.
When I magnified the stones I have I was stunned to see full SRB
cutting on the “larger” ones (the 1.25 pt diamonds) and a SRB
crown/simplified pavilion on the smaller stones (the smallest I have
is about 0.5 pt).
The stones themselves are pretty low-quality - yellowish in tone and
many have inclusions or “naturals” where the original crystal shape
was left to preserve weight. And the biggest problem with them is
their small size - a breeze or crackle in the stone paper is enough
to send them flying!
Pretty amazing when you think about the accuracy needed.