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How to Cut Obsidian

via Owyhee Gem, 1/01, Via RockCollector 3/01

Golden Sheen: Saw with the bands, as if they were a stack of plates and you wish to unstack them. Watch for "fire spots" in gold sheen. It is not plentiful, but opal-like colors do occur.

Rainbow: Cut parallel to the flow layers. These can be seen by looking at fractured surfaces using a single lamp directly overhead. Note the bands are not always straight, it may be necessary to turn the stone slightly between cuts. Examine each slab set with either water or saw oil to see if the correct angle has been obtained.

Iridescent: In cutting the two types of iridescent obsidian, orientation is important. One type is banded and the color lies in the bands. On the other type, the surface has to be chipped to find the color in the conchoidal fracture surface. Cut the banded material parallel to the bands. To get rainbow-effects, cut the stone at about 15 degrees across the bands.

Midnight Lace: Lace-pattern obsidian should be cut across the surface pattern that you want to reproduce. Sand out all scratches with grit and wet sanding (to reduce heat) before going to polish. For final polish, use felt with cerium oxide.