I once sourced them for somebody in Santiago who was adding essential oils to them to make bath salts. I have found the email I sent them.
Available from Grugo at 75 RD$ a kilo
avenida Pedro francisco Bono esquina Cuba (Santiago)
Tel 809 582 4922
You could call them and ask where they get them from if you don't want to drive there. As far as I remember they were exactly right for the purpose and good quality.
Matilda