I'm just curious. Are there many people here using boulder opal? If so, what kinds of cuts do you prefer? How many are using the matrix type with color flashes, what about larger seams accented by matrix? What kinds of sizes are you using? Etc. I just picked up some old boulder rough and I am wanting to cut to meet the market need.
Hi Derek, Many of us love Boulder Opal; and there is a good market
for it among jewelry designers. (There is -no- mass market for this
stone; because Boulder Opal is rarely available in calibrated sizes -
and never in any commercially viable quantity.)
Boulder Opal is not an easy gem to cut. It can be -very-
frustrating for folks who like predictable results. Boulder is a
gambler’s stone. The matrix may undercut. The seam of precious Opal
may take off at an odd angle. Patience is the essential tool for the
cutter who works this stone! I know of no way to predict, before
cutting, what size or shape stone is likely to appear from a chunk of
rough. The best attitude you can adopt, when beginning to cut, is to
allow the natural shape of the seam (or nodule) to suggest the
outcome. Try to expose as much precious Opal as possible, while
still leaving a structurally sound, aesthetically pleasing base.
Calibrated cutting of Boulder Opal is usually impossible; and it is
-always- wasteful. You’ll do better to let the natural shape of the
stone guide your work. (The same is true of Fire Agate…which
presents the cutter with many of the same challenges. One almost
always does better by carving the stone than by cabbing it.)
Enjoy! 
Pete
Peter B. Steiner
TripleRock Lapidary
New York, USA