World Library  
Flag as Inappropriate
Email this Article

Adularescence

Article Id: WHEBN0020848458
Reproduction Date:

Title: Adularescence  
Author: World Heritage Encyclopedia
Language: English
Subject: Optical phenomena, Moonstone (gemstone), Phenomenon, Orthoclase, Lustre (mineralogy)
Collection: Mineralogy, Optical Phenomena
Publisher: World Heritage Encyclopedia
Publication
Date:
 

Adularescence

Adularescence in a Moonstone Cabochon, Minas Gerais, Brasil (23mm)

Adularescence is an optical phenomenon, similar to labradorescence and aventurescence, that is produced in gemstones such as moonstones.

Description

The effect of adularescence, also commonly referred to as schiller or shiller, is best described as a milky, bluish luster or glow originating from below the surface of the gemstone. The schiller, appearing to move as the stone is turned (or as the light source is moved), gives the impression of lunar light floating on water (accounting for moonstone's name).[1] Though white schiller is the most common, in rarer specimens, orange or blue lusters are produced.[2]

This effect is most typically produced by adularia, from which the name derives.[3][4][5] Adularescence appears in numerous other gemstones, notably common opal, rose quartz and agate. However, due to inclusions in these other stones, the effect is displayed differently. The schiller is scattered by inclusions and appears hazy; non-hazy specimens are specially referred to as "milky". Thus, adularescence occurring in non-adularia gemstones is termed differently - "girasol effect" and opalescence (for opals only) are two such terms. When the schiller forms an indistinct band it is said to display a chatoyant effect. Only clearly defined bands are referred to as "cat's eyes".[5]

As an optical phenomenon, adularescence exists only in the presence of light; it is a product of the interaction between light and the internal microstructures of the mineral and not a property of the mineral itself. The effect is produced by alternating layers of two types (in moonstone feldspar the layers are orthoclase and albite) at a scale near the wavelength of light (ca. 0.5 micron) - this leads to light scattering and interference.[6]

References

  1. ^ Long, Bill (2004), "Varieties of Light II: Pleochroism, Nacreous, Adularescence, A(d)venturescence."
  2. ^ Semi Precious Stones Guide: List of Gemstone Phenomena
  3. ^ King, R. J. (1990). "Minerals explained 12: Alkali feldspar (Part 2)." Geology Today, 6 pp. 27-29.
  4. ^ "Adularescence," reference.com
  5. ^ a b Shipley, Robert M. (2007), Dictionary of Gems and Gemology, Read Books, p. 93.
  6. ^ Nassau, Kurt (1978). "The origins of color in minerals," American Mineralologist, vol. 63, pp. 219-229.
This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and USA.gov, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for USA.gov and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
 
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
 
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.
 



Copyright © World Library Foundation. All rights reserved. eBooks from World eBook Library are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.