Difference between revisions of "Apatite"

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{{apatite}}
 
{{apatite}}
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{|
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|-
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|[[Image:Apatite.gif|left|thumb|200px|<br /><br />Faceted Apatite <br />Photo courtesy of The Gem Trader]]
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|[[Image:Apatite2-400.jpg|left|thumb|200px|Unusual Violet Faceted Apatite <br />Photo courtesy of Jason Brim]]
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|}
  
Apatite is named "the deceiver" as it's color, refractmeter and specific gravity readings are similar to many some more gemstones as [[tourmaline]], [[topaz]], [[andalusite]] and [[danburite]].
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Apatite is named "the deceiver" as it's color, refractometer and specific gravity readings are similar to gemstones as [[tourmaline]], [[topaz]], [[andalusite]] and [[danburite]].
  
[[Image:Apatite.gif|left|thumb|250px|Faceted Apatite <br />Photo courtesty of The Gem Trader]]<br clear="left" />
 
  
 
==Diagnostics==
 
==Diagnostics==
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 +
===Appearance===
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Apatite occurs in yellow, green, violet, purple, blue, brown, colorless and pink and can be transparent to translucent.
 +
===Optic Character===
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DR, Uniaxial negative
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 +
===Refractometer===
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 +
Refractometer readings are in the range of [[tourmaline]], [[topaz]], [[andalusite]] and [[danburite]] but usually with a very low birefringence of 0.003.<br />
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Full range: n<sub>ω</sub> = 1.629 - 1.667 and n<sub>ε</sub> = 1.624 - 1.666 with a full birefringence of 0.001-0.007.<br />
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===Spectroscope===
 
===Spectroscope===
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Blue apatite will, usually, show a rare earth spectrum line in the blue (praseodymium).<br />
 
Blue apatite will, usually, show a rare earth spectrum line in the blue (praseodymium).<br />
 
Blue-green stones may have added spectrum lines in the yellow (didymium) and line(s) in the green (praseodymium).<br />
 
Blue-green stones may have added spectrum lines in the yellow (didymium) and line(s) in the green (praseodymium).<br />
Yellow gems show the rare earth spectrum of greenish-blue without the line in the blue.
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Yellow gems show the rare earth spectrum of greenish-blue without the line in the blue.<br />
 +
Neon blue stones may show rare earth spectra in the yellow.
  
===Chelsea Color Filter===
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===UV Reactions===
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*Blue: Blue to light blue (LW and SW) <br />
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*Yellow: Purplish Pink (stronger in LW)<br />
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*Green: Greenish-yellow (stronger in LW)<br />
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*Violet: Greenish-yellow (LW);Light purple (SW)
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===Chelsea Colour Filter===
  
 
Green-blue stones: green
 
Green-blue stones: green
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===Dichroscope===
 
===Dichroscope===
  
Apatite has weak pleochroism, so this tool may not be very useful except for blue stones where the dichroism is more profound.
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Apatite has weak pleochroism, so this tool may not be very useful except for blue stones where the dichroism is more profound (blue and pale yellow).
  
 
===Polariscope===
 
===Polariscope===
  
 
A nice uniaxial negative interference figure should be found.
 
A nice uniaxial negative interference figure should be found.
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 +
===Primary Sources===
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Brazil, Burma, Mexico <br />
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Violet and Purple are found in Maine and Afghanistan.
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 +
===Magnification===
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 +
Clouds of tiny white crystal inclusions may be easily observed.
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{|
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|-
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|[[Image:apatite.jpg|thumb|left|240px|Blue apatite with crystalline "fireworks" of an unidentified mineral<br />40X Magnification<br /> by Barbra Voltaire]]
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|[[Image:Apatite_accicular.jpg|thumb|left|240px|Yellow apatite with a 3-dimensional network of liquid needles <br />40X Magnification<br /> by Barbra Voltaire]]
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|}
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<br clear="left" />
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==Phenomena==
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* Cat's-eyes
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== G&G Articles on Apatite 1934-1980==
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The GIA has published all the [http://www.gia.edu/research-resources/gems-gemology/back-issue-archive/index-back-issues-1934-80.html G&G's from 1934 until 1980 online]. The organization of the list by subject was done by [http://archive.org/details/GillsHistoricalIndexToGemsAndJewelryOnline-ByJosephO.Gill2009in Joseph Gill].
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<ul><li>[http://www.gia.edu/research-resources/gems-gemology/back-issue-archive/summer-1962.pdf Summer 1962, <b>Cat's-eye apatite</b>, p. 315, 2pp.]
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</li><li>[http://www.gia.edu/research-resources/gems-gemology/back-issue-archive/summer-1963.pdf Summer 1963, <b>Yellow cat's-eye apatite</b>, p. 44, 1p.]
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</li><li>[http://www.gia.edu/research-resources/gems-gemology/back-issue-archive/winter-1965.pdf Winter 1965, <b>Cat's-eye apatite</b>, p. 372, 1p.]
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</li><li>[http://www.gia.edu/research-resources/gems-gemology/back-issue-archive/summer-1966.pdf Summer 1966, <b>A cat's-eye apatite of 220 cts</b>., p. 46, 1p.]
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</li><li>[http://www.gia.edu/research-resources/gems-gemology/back-issue-archive/winter-1972.pdf Winter 1972, <b>Rare Earth Absorption Spectra in Apatite</b>, by Anderson, p. 101, 1p.]
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</li><li>[http://www.gia.edu/research-resources/gems-gemology/back-issue-archive/winter-1972.pdf Winter 1972,<b> A 40 ct. cat's-eye apatite</b>, p. 114, 1p.]
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</li></ul>
  
 
==Sources==
 
==Sources==
  
 
* ''A Students' Guide to Spectroscopy'' (2003) - Colin Winter FGA, DGA ISBN 0954485300
 
* ''A Students' Guide to Spectroscopy'' (2003) - Colin Winter FGA, DGA ISBN 0954485300
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* [http://www.amazon.com/gp/product/0195149106?ie=UTF8&tag=gemsandwhywelove&link_code=as3&camp=211189&creative=373489&creativeASIN=0195149106 Introduction to Optical Mineralogy'' 3rd edition (2003), Prof. W.D. Nesse]

Latest revision as of 10:49, 13 August 2012

Apatite
Chemical composition Ca5(PO4)3(F,Cl,OH)
Crystal system Hexagonal
Habit Prismatic
Cleavage Imperfect, basal
Fracture Conchoidal
Hardness 5
Optic nature Uniaxial -
Refractive index 1.63-1.64
Birefringence 0.003
Dispersion Low, 0.013
Specific gravity 3.2
Lustre Vitreous
Pleochroism Weak


Faceted Apatite
Photo courtesy of The Gem Trader
Unusual Violet Faceted Apatite
Photo courtesy of Jason Brim

Apatite is named "the deceiver" as it's color, refractometer and specific gravity readings are similar to gemstones as tourmaline, topaz, andalusite and danburite.


Diagnostics

Appearance

Apatite occurs in yellow, green, violet, purple, blue, brown, colorless and pink and can be transparent to translucent.

Optic Character

DR, Uniaxial negative

Refractometer

Refractometer readings are in the range of tourmaline, topaz, andalusite and danburite but usually with a very low birefringence of 0.003.
Full range: nω = 1.629 - 1.667 and nε = 1.624 - 1.666 with a full birefringence of 0.001-0.007.


Spectroscope

The spectroscope is a good diagnostic tool in seperating apatite from gemstones as tourmaline and topaz.

Blue apatite will, usually, show a rare earth spectrum line in the blue (praseodymium).
Blue-green stones may have added spectrum lines in the yellow (didymium) and line(s) in the green (praseodymium).
Yellow gems show the rare earth spectrum of greenish-blue without the line in the blue.
Neon blue stones may show rare earth spectra in the yellow.

UV Reactions

  • Blue: Blue to light blue (LW and SW)
  • Yellow: Purplish Pink (stronger in LW)
  • Green: Greenish-yellow (stronger in LW)
  • Violet: Greenish-yellow (LW);Light purple (SW)


Chelsea Colour Filter

Green-blue stones: green

Dichroscope

Apatite has weak pleochroism, so this tool may not be very useful except for blue stones where the dichroism is more profound (blue and pale yellow).

Polariscope

A nice uniaxial negative interference figure should be found.

Primary Sources

Brazil, Burma, Mexico
Violet and Purple are found in Maine and Afghanistan.

Magnification

Clouds of tiny white crystal inclusions may be easily observed.

Blue apatite with crystalline "fireworks" of an unidentified mineral
40X Magnification
by Barbra Voltaire
Yellow apatite with a 3-dimensional network of liquid needles
40X Magnification
by Barbra Voltaire


Phenomena

  • Cat's-eyes

G&G Articles on Apatite 1934-1980

The GIA has published all the G&G's from 1934 until 1980 online. The organization of the list by subject was done by Joseph Gill.

Sources