Feldspar, Spodumene, Diopside and more

Feldspar, Spodumene, and Diopside

Largest Consumers

• Moonstone: popular in Europe and the US in the early 1900s
• Sunstone: popular in China, and among upscale jewelry designers, collectors, and gem carvers in the US
• Kunzite: popular in the US and Japan among collectors and designers

Mohs Scale

• Moonstone: soft, 6 to 6.5
• Labradorite: fairly soft, 6, cleaves easily
• Amazonite: 6, with 2 cleavage directions
• Spodumene: 6.5 to 7, with cleavage in 2 directions
• Chrome Diopside: toughness is poor, hardness ranges from 5.5 to 6, with 2 cleavage directions

Variety/Species/Group

• Feldspar Group: includes Moonstone, Sunstone, and Amazonite
• Pyroxene Group: includes Spodumene and Diopside
• Spodumene: three varieties - hiddenite, triphane, and kunzite

Color/Hue Range/Value

• Moonstone: ranges from semitransparent to opaque, with colors including blue, silver, white, green, yellow, brown, and gray
• Labradorite: dark gray body color with spectral colors of blues and greens
• Sunstone: yellow, orange, or brown body color, with aventurescence
• Amazonite: white, light orange, or pink, with grid-like white streaks and faint sheen
• Kunzite: light pink to intense pink and violetish purple
• Chrome Diopside: transparent, medium-dark, vivid green

Chemical Composition

• Feldspar: contains aluminum, oxygen, and silicon, with potassium, calcium, and sodium as major components
• Moonstone: composed of two feldspar species, orthoclase and albite
• Labradorite: plagioclase feldspar, with fine, microscopic, intergrown layers of albite and other plagioclase
• Sunstone: orthoclase sunstone, with monoclinic crystal system
• Amazonite: microcline feldspar, with potassium-rich alkali feldspar series
• Chrome Diopside: contains trace elements chromium or vanadium

Possible Phenomena

• Moonstone: adularescence, chatoyancy, and four-rayed asterism
• Labradorite: labradorescence
• Sunstone: aventurescence, sparkly, metallic luster
• Chrome Diopside: four- or six-rayed asterism, or chatoyancy against a dark green to black background

Clarity Characteristic

• Moonstone: two cleavage directions, tiny tension cracks called centipedes
• Sunstone: inclusions can be hematite, copper, or other minerals
• Kunzite: cleavage in 2 directions, color tends to fade with exposure to bright light or high heat

Common Cuts

• Moonstone: cabochon, beads, carvings, and calibrated stones
• Labradorite: pendants, carved and polished objects, and tile
• Chrome Diopside: cut with shallow pavilions to avoid darkness

Countries of Origin

• Moonstone: Sri Lanka, Southern India, Myanmar, and India

• Labradorite: Finland, Madagascar

• Sunstone: US (Oregon)

• Amazonite: Brazil, India, Madagascar, Norway, Russia, and the US

• Kunzite: Afghanistan, Brazil, Madagascar, and the US (California)

• Chrome Diopside: eastern Siberia and Russia### Feldspar Group

• Includes Moonstone, Sunstone, and Amazonite

• Moonstone:

  • Range from semitransparent to opaque, with blue, silver, or white adularescent effect
  • Bodycolors vary widely from green, yellow, to brown, or gray to nearly black
  • Finest are colorless, semitransparent, with a vivid blue adularescence
  • Rainbow Moonstone: displays multicolored adularescence
  • Parrot Green Moonstone: bright green body color, adularescence floats in this sea of green

• Sunstone:

  • Yellow, orange, or brown bodycolor, not all sunstones are aventurescent
  • Appearance of phenomenon depends on the size of the inclusions
  • Small inclusions create a reddish or golden sheen on top of any body color
  • Larger inclusions create attractive, glittery reflections
  • Oregon Sunstone: range includes colorless, pale yellow, pink, orange, red, green, and blue-green with copper inclusions

• Amazonite:

  • White, light orange, or pink, known as amazonite or Amazon stone in its light green to greenish blue hues
  • Grid-like white streaks and faint sheen

Pyroxene Group

• Includes Spodumene & Diopside
• Kunzite:
  • Light pink is most common, but top kunzite colors are intense pink and intense violetish purple
  • Cleavage in 2 directions, color tends to fade with exposure to bright light or high heat
• Chrome Diopside:
  • Transparent, medium-dark, vivid green, very little eye-visible inclusions
  • Can occur with four- or six-rayed asterism or chatoyancy against a dark green to black background

Treatments and Imitations

• Sunstone: not treated, a big selling point of the natural "Oregon" sunstone
• Kunzite: irradiation followed by heat treatment can create kunzite's attractive rosy color from colorless or light-colored spodumene
• Sunstone: imitation material is a manmade glass called goldstone, often brownish orange with translucent, small, flat copper inclusions
• Kunzite: imitations include glass, synthetic sapphire, and synthetic spinel

Market and History

• Moonstone: popular in both Europe and the United States in the early 1900s
• Sunstone: consumers in China show a strong interest, current market is a specialized one, consisting of upscale jewelry designers, collectors, and gem carvers, as well as tourists to the Oregon desert seeking a precious all-American souvenir
• Kunzite: collectors' stone status in the US and Japan, periods of strong supply, it's popular w/designer and mass-market jewelry styles
• Controversy around Andesine: claimed to be from Congo, Tibet, and Inner Mongolia was actually all from a single unknown source, and that was actually treated through a heating process diffusing copper into yellow andesine and labradorite feldspars