Dear Mike,
Please do not work with Hydrofloric Acid. it is the most
dangerous acids around, and if something goes wrong, it is next
to impossible to neutralize it. and this is why you can not find
it. I had a mixture of nitric and hydrochloric acid blown in my
face while treating emeralds. it was not fun!, if you are not in
a rush, choose mild acid, and give it time (few days). the only
place that I know where they use Hydrofloric Acid is in Burma
,where they clean Mong Hsu Ruby rough and you would not like to
know the life span and the age of the people doing it, the only
reason is that in this rough has an iron core that can be remove
ONLY with this horrible stuff. unless you can afford high quality
protection gear and work according standard industrial procedure,
it is not worth the risk!
Hemi Englisher, GemCal Co.
4/22 Rajple 2 Cha-Am,
Petchaburi 76120 Thailand.
https://www.ganoksin.com/kosana/gemcal/spinel.htm