Definition

1. Noun:
   • A translucent mineral: A naturally occurring solid substance that allows light to pass through it diffusely, composed primarily of hydrated silica (silicon dioxide with water).
   • A gemstone: Some varieties of this mineral, prized for their play of color, are cut and polished for use in jewelry.

Examples of Usage

• Noun:
  • The museum displayed a beautiful fire opal from Australia.
  • Her ring featured a central opal surrounded by diamonds.
  • Opal is the birthstone for October.

Advanced Usage

• "Precious opal": Refers specifically to opal that exhibits a characteristic "play-of-color," where flashes of spectral colors change with the angle of view.
  • The value of a precious opal depends on the brilliance and variety of its play-of-color.
• "Common opal" (or "potch"): Refers to opal that lacks this play-of-color and is usually milky or dull in appearance.
  • Common opal is often used for carvings or as an ornamental stone.

Variants and Related Words

• Opalescent (adj): Exhibiting a milky iridescence or play of colors like that of an opal.
  • The vase had an opalescent sheen.
• Opaline (adj): Resembling opal, especially in its appearance or milky iridescence.
  • The opaline glass diffused the light softly.

Synonyms

• Gemstone: A precious or semi-precious stone, especially when cut and polished for jewelry. (This is a broader category that includes opal).
• Hydrated silica: The chemical description of opal's primary composition.

Related Phrases and Terms

• "Play-of-color": The optical phenomenon, caused by the diffraction of light, that gives precious opal its unique iridescent appearance.
  • The opal's play-of-color shifted from green to blue as she moved her hand.
• "Fire opal": A variety of opal, often orange or red, that may or may not show play-of-color but is valued for its fiery body color.
• "Black opal": A rare and valuable variety of precious opal with a dark body tone (dark blue, gray, or black) that makes the play-of-color particularly vivid.
• "Opal doublet/triplet": Composite stones where a thin slice of precious opal is glued to a backing material (doublet) or also capped with a clear quartz or glass dome (triplet) to enhance durability and appearance.

Noun

1. a translucent mineral consisting of hydrated silica of variable color; some varieties are used as gemstones