This sugar-acid-treated Andamooka matrix opal certainly resembles fine black opal. However, if you look closely at the black areas you'll see that this is a treated matrix opal. "Andamooka matrix opal" by Dpulitzer. Licensed under CC BY-SA 3.0.
Translucent Black Play-of-Color Opal Stone Cabochon
This Andamooka matrix opal certainly resembles fine black opal. However, if you look closely at the black areas you'll see this matrix opal received a sugar-acid treatment. "Andamooka matrix opal," photo by Dpulitzer. Licensed under CC By-SA 3.0.
Article: Opal Treatments: How to Detect Treated Opals
Credit: Dpulitzer
| Gemstone | Opal Stone |
| Natural or man made | Natural |
| Gem State | Cabochon |
| Color | Black |
| Transparency | Translucent |
| Photo phenomena | Play of Color |