Feldspar, Spodumene, and Diopside: Key Concepts

Feldspar, Spodumene, and Diopside

• Feldspar, spodumene, and diopside are soft gems with cleavage in two directions, requiring protective settings.
• Feldspars are the most widespread minerals on earth.
• Moonstone, a type of feldspar, exhibits adularescence due to the scattering of light by stacked, alternating mineral layers.

Moonstone

• The finest moonstones have a colorless, semitransparent to nearly transparent appearance and vivid blue adularescence.
• Moonstones are readily available in modestly priced, calibrated sizes, but rare and expensive in fine quality.
• The most common cutting style for moonstone is the cabochon.

Labradorite

• Labradorite's phenomenal colors are caused by interference of light reflecting off the gem's layered structure.
• The most prized labradorite type is "spectrolite," a phenomenal labradorite with brilliant spectral hues.

Spodumene

• Kunzite, a type of spodumene, is most commonly light pink, but its most valuable colors are intense pink and intense violetish purple.
• Light-colored or colorless spodumene is irradiated and then carefully heated to produce kunzite's rosy color, but the color can fade under heat or bright light.

Diopside

• Chrome diopside is an effective emerald alternative due to its high clarity and lack of treatment.

Key Terms

• Blue sheen: Trade term for a highly prized, vivid blue adularescence displayed by the finest moonstone.
• Goldstone: An imitation of aventurine feldspar made of glass containing small copper crystals.