Post by stoner on Jul 22, 2006 16:41:08 GMT -5
Hey all, I found this little tidbit of info and thought it was interesting enough to share here, since we all love those little dendrites found in Montana agates.
It has always been a mystery how the peculiar little scenes got inside a rock as hard as agate. It is the claim of geologists that the spots were caused by infinitely minute seams or fissures in the softer parts of the rock being filled with metallic oxides when the world was young. These oxides made four different colors that form various combinations of color when blended together, or appear in single colors in each rock.
The red color is oxide of iron. The black is oxide of manganese. The green is oxide of copper. The blue is oxide of nickel. This theory has been elaborated by the help of high-powered microscopes which show the tracings of little canals so close the naked eye could not detect it; but the oxides remained staining the rocks in wonderful designs. The fernlike and branch effects of the trees grass and shrubbery, come from the fact that the tiny canals branched out in various subdivisions forming smaller canals for a common center. In addition to these canals, the rock became flawed through shrink-age while passing through a period of evaporation which, according to scientists, has taken more than three million years to reduce the stone to the hardness of 7 on the Mohs scale.
These canals and flaws have been perfectly healed by soft silicate formations of which the stone is a part, and the evaporation has caused the oxides to take on such forms as seen on the window after a frosty night. Technically, Montana agate is known as "dendritic" agate, and the moss spots are called "dendrites".
It is the third hardest stone in the world, and is cut only with a diamond saw. There can never be two pieces alike even though cut from the same stone.
(From The Petrified Digest May 2001,
via Rock Writings & others,
via Rocket City Rocks & Gems, 3/2000),
via Stoney Statement 6/2001.
It has always been a mystery how the peculiar little scenes got inside a rock as hard as agate. It is the claim of geologists that the spots were caused by infinitely minute seams or fissures in the softer parts of the rock being filled with metallic oxides when the world was young. These oxides made four different colors that form various combinations of color when blended together, or appear in single colors in each rock.
The red color is oxide of iron. The black is oxide of manganese. The green is oxide of copper. The blue is oxide of nickel. This theory has been elaborated by the help of high-powered microscopes which show the tracings of little canals so close the naked eye could not detect it; but the oxides remained staining the rocks in wonderful designs. The fernlike and branch effects of the trees grass and shrubbery, come from the fact that the tiny canals branched out in various subdivisions forming smaller canals for a common center. In addition to these canals, the rock became flawed through shrink-age while passing through a period of evaporation which, according to scientists, has taken more than three million years to reduce the stone to the hardness of 7 on the Mohs scale.
These canals and flaws have been perfectly healed by soft silicate formations of which the stone is a part, and the evaporation has caused the oxides to take on such forms as seen on the window after a frosty night. Technically, Montana agate is known as "dendritic" agate, and the moss spots are called "dendrites".
It is the third hardest stone in the world, and is cut only with a diamond saw. There can never be two pieces alike even though cut from the same stone.
(From The Petrified Digest May 2001,
via Rock Writings & others,
via Rocket City Rocks & Gems, 3/2000),
via Stoney Statement 6/2001.