I buy my clear quartz in rods and cut it to the proper thickness for
making triplets. I cut it about 1.5 mm, then flatten the cut side on
a flat lap.
I buy it from http://www.creativegems.com
P.O. Box 518
Seagoville, Tx 75159
Toll Free 1-888-287-3445
A rod is $6.00, 6+ inches long, and about.5 inch to.75 inch in
width. I have had great customer service, including over night
shipping when I was in a triplet making class in Grady and Phyllis are
wonderful people and I'm sure you will be happy with their product
and service. They also have (or used to have) precut and pre-shaped
caps in different sizes for triplets if you don't want to have to cut
them, but I prefer the rods, much more versatile.
Love and God Bless