Difference between revisions of "Black opal"
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| Line 10: | Line 10: | ||
== Risks == | == Risks == | ||
| − | Chronic inhalation may cause lung damage | + | * Chronic inhalation may cause lung damage |
| − | + | * Dehydration may cause surface cracking | |
| − | Dehydration may cause surface cracking | ||
== Physical and Chemical Properties == | == Physical and Chemical Properties == | ||
| − | Massive with no crystalline structure. Cleavage=none Luster = vitreous to pearly. Fracture = conchoidal. Streak = white | + | * Massive with no crystalline structure. |
| − | + | * Cleavage=none | |
| − | Iridescent. Fluoresce=usually white or pale green, some samples phosphoresce | + | * Luster = vitreous to pearly. |
| + | * Fracture = conchoidal. | ||
| + | * Streak = white | ||
| + | * Iridescent. | ||
| + | * Fluoresce=usually white or pale green, some samples phosphoresce | ||
{| class="wikitable" | {| class="wikitable" | ||
| Line 25: | Line 28: | ||
|- | |- | ||
! scope="row"| Density | ! scope="row"| Density | ||
| − | | 1.98-2.25 | + | | 1.98-2.25 g/ml |
|- | |- | ||
! scope="row"| Refractive Index | ! scope="row"| Refractive Index | ||
Latest revision as of 08:46, 8 May 2022
Description
An Opal with vivid iridescent colors on a dark background. Black opals were first discovered in 1902 at Lightning Ridge in New South Wales, Australia. Black opals display different color patterns depending on the viewing angle. The colors depend on the crystal size within the stone. When the particles are small, some purple can be seen. Medium sized particles diffract green and larger particles show red.
Synonyms and Related Terms
ópalo negro (Esp.); opala negra (Port.)
Risks
- Chronic inhalation may cause lung damage
- Dehydration may cause surface cracking
Physical and Chemical Properties
- Massive with no crystalline structure.
- Cleavage=none
- Luster = vitreous to pearly.
- Fracture = conchoidal.
- Streak = white
- Iridescent.
- Fluoresce=usually white or pale green, some samples phosphoresce
| Mohs Hardness | 5.5 - 6.5 |
|---|---|
| Density | 1.98-2.25 g/ml |
| Refractive Index | 1.42-1.47 |
Resources and Citations
- Mineralogy Database: Opal
- Wikipedia: http://en.wikipedia.org/wiki/Opal (accessed Oct. 12, 2005)
- Yasukazu Suwa, Gemstones: Quality and Value, Volume 1, Sekai Bunka Publishing Inc., Tokyo, 1999
- Michael O'Donoghue and Louise Joyner, Identification of Gemstones, Butterworth-Heinemann, Oxford, 2003