Gemstone Faceting Diagrams by Material
A pavilion angle optimized for sapphire windows badly in quartz, while quartz angles waste the refractive power of CZ and moissanite. Choose your rough gemstone material below to browse diagrams engineered specifically for its refractive index and critical angle.
Corundum (Sapphire & Ruby)
Blue sapphire, Padparadscha, ruby, Montana sapphire, lab-grown corundum
Corundum (sapphire and ruby, RI 1.76, critical angle 34.6°) is the benchmark colored gemstone for custom faceting: Mohs 9 durability paired with enough refractive power to support bold contrast patterns without pavilion leakage.
Quartz, Amethyst & Citrine
Amethyst, citrine, ametrine, smoky quartz, rose quartz, rock crystal
Quartz (RI 1.54) has a steep 40.5° critical angle—which is why generic faceting patterns cut at 39°–41° suffer from washed-out tilt windows right through the table.
Beryl (Aquamarine, Morganite, Heliodor & Emerald)
Aquamarine, morganite, emerald, heliodor, goshenite
Pastel beryls like aquamarine and morganite live or die by light path length: if the pavilion leaks below beryl's 39.3° critical angle, pale rough loses half its face-up color saturation.
Topaz & Tourmaline
Swiss & London blue topaz, imperial topaz, green & pink tourmaline, rubellite, indicolite
Sitting around RI 1.61–1.62 (critical angle ~38.4°), topaz and tourmaline offer noticeably crisper contrast and wider angular headroom than quartz—provided pavilion tiers respect dark c-axis absorption in tourmaline.
Spinel & Garnet (Rhodolite, Malaya, Pyrope)
Red, pink, grey & cobalt spinel, rhodolite garnet, Malaya garnet, grossular/tsavorite
Spinel and pyralspite/grossular garnets (RI 1.72–1.74, critical angle 35.5°) are singly refractive favorites among precision cutters—rewarding well-tuned pavilion geometry with vivid, zero-doubling flash.
Cubic Zirconia (CZ) & YAG/GGG Synthetics
Colored & white cubic zirconia (CZ), high-RI lab crystals
With RI 2.15, a forgiving 27.7° critical angle, and 0.060 dispersion (higher than diamond), cubic zirconia unlocks dramatic optical patterns that lower-RI natural stones simply cannot sustain.
Natural & Lab-Grown Diamond
Lab-grown CVD/HPHT diamond, natural diamond, strontium titanate
At RI 2.42 (critical angle 24.4°), rays exit the crown with steep refraction fans where sub-degree angle shifts separate world-class scintillation from flat, washed-out glare.
Synthetic Moissanite (Silicon Carbide)
Colorless, blue, green, cyan & champagne lab-grown moissanite
Moissanite's extreme RI 2.67 (critical angle 22.0°) and 0.104 dispersion mean diamond-angle cuts often look overly busy or milky—whereas geometry tuned expressly for RI 2.67 delivers jaw-dropping contrast and controlled fire.