An iridescent blue sample of precious opal. Opal is composed of microspheroids of hydrous silicon oxide. It is the refraction of light within these spheroids which gives the mineral its iridescent,mother-of- pearl-like sheen. Opal never occurs in a crystaline form,but as small veins,globules and crusts. Several other varieties occur; colourless,milky white,blue,red (fire opal) and black types and also a type of fossilised wood know as wood opal. Black and fire opals are particularly valued as gemstones | |
Lizenzart: | Lizenzpflichtig |
Credit: | Science Photo Library / Land, Martin |
Bildgröße: | 5052 px × 3714 px |
Modell-Rechte: | nicht erforderlich |
Eigentums-Rechte: | nicht erforderlich |
Restrictions: | - |