100% silk gauze is for doing very fine work because the fabric itself is very fine. It can have different counts, the finest count I've seen is 60 threads to the inch. You can use silk gauze for delicate insect wings in stumpwork, for miniature embroideries etc. Au Ver a Soie is one company I know that makes the fabric. One supplier is Sewandso in the UK. Do an internet search for your own location.