Glass (Glass facet) / Obsidian
Glass (Glass facet) – Leaded glasses are available in all types of colors and refractive indexes. I do not recommend cutting leaded glass because of the health dangers of the lead.
- “Obsidian,” showing conchoidal fractures, by Kevin Walsh is licensed under CC By 2.0
Obsidian (volcanic siliceous glass)
Type: Apache Tears
Color: Dark gray to brownish-gray. May be transparent, translucent, or nearly opaque.
Moh’s Hardness: 5.5
Refractive Index: 1.48-1.51
Critical Angle: 42.51°
Specific Gravity: 2.3-2.6
Fracture: Large conchoidal
Heat Sensitivity: Moderate
Crystal Structure: Amorphous
Treatments: Generally none
What I prefer to polishing with: Glass is not something I cut, recommended polishes, cerium oxide on most common polishing laps.
Jeff’s Comments: Cuts pretty easily, and can be a tough to polish. Watch the heat when dopping. Typically has silk and cleavage problems. Apache tears may have internal pressures that can be released during sawing or cutting, causing the material to literally fly apart. Use eye protection… . Like most glass Apache tears also tend to contain bubbles and large stones are usually too dark unless cut from the lightest material.
Design Notes: About any shallow Quartz designs will work well.