Origin of Precious Opal

Nature ◽  
1966 ◽  
Vol 209 (5018) ◽  
pp. 13-16 ◽  
Author(s):  
P. J. DARRAGH ◽  
A. J. GASKIN ◽  
B. C. TERRELL ◽  
J. V. SANDERS
Keyword(s):  
Precious Opal

The Origin of the Colour in Precious Opal

1954 ◽  
Vol 4 (5) ◽  
pp. 200-210
Author(s):  
G. F. Leechman
Keyword(s):  
Precious Opal

Further Notes on the Cause of Colours in Precious Opal

1954 ◽  
Vol 4 (7) ◽  
pp. 288-291
Author(s):  
G. F. Leechman
Keyword(s):  
Precious Opal

The Precious Opal

1990 ◽  
Vol 18 (4) ◽  
pp. 56-58
Author(s):  
Carole Bellacera
Keyword(s):  
Precious Opal

Colour of Precious Opal

Nature ◽  
1964 ◽  
Vol 204 (4964) ◽  
pp. 1151-1153 ◽  
Author(s):  
J. V. SANDERS
Keyword(s):  
Precious Opal

Formation of Precious Opal

Nature ◽  
1965 ◽  
Vol 207 (4996) ◽  
pp. 472-473 ◽  
Author(s):  
R. K. ILER
Keyword(s):  
Precious Opal

scholarly journals Self-assembly in the growth of precious opal

2010 ◽  
Vol 312 (3) ◽  
pp. 391-396 ◽  
Author(s):  
A.M. Stewart ◽  
Lewis T. Chadderton ◽  
Brian R. Senior
Keyword(s):  
Self Assembly ◽  
Precious Opal

Electron Microscopy of Precious Opal

1968 ◽  
Vol 26 ◽  
pp. 458-459
Author(s):  
Eugene J. Amaral ◽  
Robert C. Rau
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Visible Light ◽  
Amorphous Silica ◽  
Three Dimensional ◽  
Silica Spheres ◽  
Sphere Diameter ◽  
Transmission Electron ◽  
Uniform Diameter ◽  
Precious Opal

Replica and transmission electron microscopy have been used to study the microstructure of precious opal. This mineral is an amorphous silica which is often prized as a gemstone because of its vivid display of iridescent colors when viewed in visible light. For the present study, specimens were examined in fractured, polished, and etched conditions.As shown in the figures, precious opal consists of many tiny silica spheres, of essentially uniform diameter, that have been deposited in an orderly array before silica cementation. Regularly spaced interstitial voids resulting from the ordered packing serve as a three dimensional diffraction grating for visible light, thus giving rise to the characteristic play of colors. The separation of the voids is controlled by sphere diameter, and determines the maximum wavelength of visible light diffracted. Thus specimens consisting of larger spheres diffract higher order colors (longer wavelengths) than specimens consisting of smaller spheres. For example, the specimen shown in Fig. 1 contained spheres of approximately 2700 Å diameter and diffracted all visible colors up through red, while the specimen shown in Fig. 2 contained spheres of approximately 2000 Å diameter and diffracted only blues and greens.

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