a type of quartz known as striated
Agate consists of silicon and
oxygen, giving it the chemical formula SiO2.
It has a specific gravity of 2.58-2.64, and a
hardness of 7-9 on the Mohs Scale. The mineral was named by Greek
philosopher Theophrastus, who found agates along
the river Achates sometime between the 4th and
3rd centuries B.C.
Agate forms when silica in
solution seeps into a cavity in lava and hardens
in successive layers. Agate is harder than lava,
so as the lava wears away the agates are left
behind, usually as rounded pebbles. Agates are
usually found in stream beds and gravel banks
where volcanic activity was once common,
especially in Brazil, Egypt, Germany, India,
Italy, Mexico, Nepal, and the Lake Superior
region of the United States.
Agate was once believed to have
magical powers, capable of making someone tell
the truth and of improving one's memory and
concentration. It is the mythical birthstone for
September, the birthstone for the Zodiac sign
Gemini, and the traditional gemstone gift for
12th and 14th wedding anniversaries.
E.L. Jordan. Hammond Nature Atlas of
North America. New York: Hammond
Bernardine Fine Art Jewelry www.bernardine.com/gemstones/agates.htm
International Colored Gemstone
Mohs Hardness Scale
Questions or comments about