Difference between revisions of "Agate"

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(Moss Agate)
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===Moss Agate===
 
===Moss Agate===
This variety is called "moss" agate because of the inclusions (chlorite, clays, various oxides/hydroxides, etc.) in transparent/translucent chalcedony. The final effect makes the stone resemble "moss". Depending on the inclusions the moss can show different colors, with green and red as the most common. They usually take a good polish and make attractive stones.
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This variety is called "moss" agate because of the inclusions (chlorite, clays, various oxides/hydroxides, etc.) in transparent/translucent chalcedony. The final effect makes the stone resemble "moss". Depending on the inclusions the moss can show different colors, with green/brown and red as the most common. They usually take a good polish and make attractive stones.
 
[[Image:Agt0007.JPG|thumb|left|240px|Moss Agate from a Priday thunderegg (Oregon). Green moss. ''(Image courtesy of Marco Voltolini)'']]
 
[[Image:Agt0007.JPG|thumb|left|240px|Moss Agate from a Priday thunderegg (Oregon). Green moss. ''(Image courtesy of Marco Voltolini)'']]
 
[[Image:Moss2.JPG|thumb|left|240px|Detail of a Moss Agate from a Priday thunderegg (Oregon). ''(Image courtesy of Marco Voltolini)'']]
 
[[Image:Moss2.JPG|thumb|left|240px|Detail of a Moss Agate from a Priday thunderegg (Oregon). ''(Image courtesy of Marco Voltolini)'']]

Revision as of 13:27, 26 September 2010

Agate
Chemical composition Silicon dioxide SiO2
Crystal system Trigonal
Habit Aggregate
Fracture Conchoidal
Hardness 6.5-7
Refractive index 1.535 - 1.539
Specific gravity 2.60
Lustre Vitreous

Agate is a variety of banded microcrystalline quartz, or chalcedony. There are countless varieties of agate usually named after their physical characteristics or location of origin. The layers of agate form as layers of chalcedony line a cavity (or vug) in a host rock. Since the 12th century, agate has been attributed with the power of improving one's disposition as well as their eyesight. These beliefs still carry on today. One claim for agate was stated in The Book of Saxon Leechdoms written in 1864, where it was written that agate prevents harm from thunder, sorcery, demonic possession, poison and drunkenness!


Varieties

Moss Agate

This variety is called "moss" agate because of the inclusions (chlorite, clays, various oxides/hydroxides, etc.) in transparent/translucent chalcedony. The final effect makes the stone resemble "moss". Depending on the inclusions the moss can show different colors, with green/brown and red as the most common. They usually take a good polish and make attractive stones.

Moss Agate from a Priday thunderegg (Oregon). Green moss. (Image courtesy of Marco Voltolini)
Detail of a Moss Agate from a Priday thunderegg (Oregon). (Image courtesy of Marco Voltolini)
Detail of a Moss Agate from a Priday thunderegg (Oregon). (Image courtesy of Marco Voltolini)


Moss Agate from Oregon, red moss. (Image courtesy of Marco Voltolini)
Moss Agate from Oregon, red moss, detail. (Image courtesy of Marco Voltolini)
Moss Agate from Oregon, red moss, detail. (Image courtesy of Marco Voltolini)