October 27-28—SACRAMENTO, CALIFORNIA: 82nd Annual Gem, Jewelry, Mineral and Rock Show; Sacramento Mineral Society; Sat. 10-5, Sun. 10-4
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 Post subject: Re: Colour Change Statement Note
PostPosted: Thu Jul 08, 2010 12:21 pm 
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Joined: Mon May 14, 2007 11:00 am
Posts: 1133
Location: Monterey, CA
Quote:
A view through a Chelsea filter can cause various emeralds to become color change stones, yet we know they are not classified as such.

Strictly speaking, ALL gemstones are "color change or color shift".
When one changes the "color" (compsition) of the light source, the eye will note a change in its apparent color. (All amethysts are color "change or shift".It's just a matter of how much the color changes or shifts and the eyesight of the observer.

Quote:
Filters should not of neccessity be the arbiter for the C-chg call. A pocket torch is still $1 and the eyeball & brain the judge.

Without recognized standards of lighting and definitions of color, as well as a system of quantitative measurements, this entire subject is can never be resolved. It will always remain subjective—exactly like the vendors of such material want. Without standards, everyone's opinion is equally valid.


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 Post subject: Re: Colour Change Statement Note
PostPosted: Thu Jul 08, 2010 1:29 pm 
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Joined: Fri Feb 24, 2006 1:20 am
Posts: 2719
Location: Southern California, U.S.A.
Bill Hanneman wrote:
Without standards, everyone's opinion is equally valid.


Especially on the internet! :lol:

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Rick Martin

www.artcutgems.com


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