Product Details: + Gemstone: Boulder Opal + Color: Grey/Blue + Shape: Half Moon + Strand Length: 8 Inches + Size : 15MM + Treatment: Natural + Drill Orientation: Straight Drilled + Hole Size: 0.6MM + Approx. Beads: 20 Beads + Approx. Weight: 15 Grams For Wholesale pricing, contact us via email at firstname.lastname@example.org or call us at 347-656-4080. Boulder opal is a rock that contains thin seams and patches of opal surrounded by or attached to its natural host rock. The cutter studies this rock and decides how to cut the best possible gem. That gem might be cut to display seams and patches of precious opal as they appear within their natural host rock. Alternatively, the gem might be cut in an orientation that presents a thin seam of precious opal as the face of the gem with its natural host rock as a backing.