Difference between revisions of "Black opal"

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== Risks ==
 
== Risks ==
  
Chronic inhalation may cause lung damage   
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* 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"
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|-
 
|-
 
! scope="row"| Density
 
! scope="row"| Density
| 1.98-2.25
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| 1.98-2.25 g/ml
 
|-
 
|-
 
! scope="row"| Refractive Index
 
! scope="row"| Refractive Index

Latest revision as of 07:46, 8 May 2022

Tiffany necklace
MFA# 2017.1328

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
  • 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