The "smallest possible mass" of a black hole depends on your personal definition of what a black-hole IS...

In MY opinion, a super-massive-object is not yet a black-hole UNTIL its gravity
reaches the point where light can no longer escape. Then it IS a black-hole.

So with a bit of net-research, surely there is some information somewhere that
can give a genuine value to the strength of gravity required to stop light.
And from that value it should be possible to calculate how much mass is required
to generate that much gravity.

To the best of my knowledge, a neutron star is a super-heavy-object.
So dense it can nearly be called a single super-massive-ATOM!!
But it will never evolve into a black-hole I believe.
Both neutron stars AND black holes are generated at the heart of a super-nova.
Supernova's can create neutron stars when they are big enough 'crush' their own cores into a solid mass.
But sometimes, if they are big enough, they will create a black-hole instead.
I dont know if the reason for one or the other is due to the amount of mass,
that gets compacted, or if it is the power of the explosion that makes the difference.
I suspect its a combination of both...

So, to my mind, black-holes and neutron stars are related, but only as separate
branches on a star's evolution, not one leading to the other.

So I dont think "small black holes" are possible, the definition makes no sense.
But the LHA does create small amounts of anti-matter (which has nothing to do with back-holes BTW),
and super-dense-particles (call these super-dense-particles "micro black-holes" if you like).
The anti-matter rapidly "delf-destruct"s, and is such small amounts it is harmless.
And (I believe) the super-dense-particles "evaporate" as they are pulled apart by
the gravitational/elelctrical charges of the nearby (and far more numerous) atoms of normal(unmodified) matter.