Opal Gemstone Beads from Rings & Things: Opal beads have the same basic chemical composition as quartz, but usually contain 6 - 10% water. Because of this, opal jewelry components should be protected from heat and strong light. Loss of water can cause opals to crack and/or lose iridescence. Opal beads can be oiled to prevent dehydration. Make sure to keep your opal beads away from detergents, ultrasonic cleaners, metal polish, acids and strong solvents.
Precious opal contains flashes of light; common opal does not, but both are hydrated amorphous Silicon Dioxide.
African green opal beads (aka Australian green opal and petrified green opal) come in several pretty shades of brown and green. They sometimes display black or brown dendrites (fern-like inclusions).
Making October birthstone jewelry or gifts for men? Wood opal's neutral, earthy colors make it an excellent option for guys.
Manmade Opalite... see below.