Quartz (SiO2) [Agate, jasper, chalcedony]
|Milky quartz vein (massive quartz) in Mary Ellen gold mine, |
WY. When this rock weathers out, it forms massive pieces of
quartz referred to as rock crystal.
There are several minor ornamental stones of chatoyant quartz. Such quartz contains parallel fibrous mineral inclusions that exhibit wavy reflections as they are rotated in light (Hurlbut and Klein 1977). Rather than fibrous mineral inclusions, Koivula and Tannous (2004c) associate chatoyancy with “thin hollow tubes resulting from growth blockage (growth tubes) and/or post-growth dissolution features (etch tubes)”. Chatoyancy is also seen in Tiger’s Eye, a variety of cryptocrystalline quartz.
|Silicified and polished dinosaur bone from the Morrison Formation|
|Youngite specimen from the Hartville area.|
- banded agate – an agate that exhibits distinct color banding.
- fortification agate – an agate with banding that flows outward into several points within a nodule to provide the appearance similar to a medieval fortress.
- eye agate – an agate with concentric banding surrounding a point in the center that gives the appearance of an eye.
- agate breccia – an agate formed of broken broken lithic fragments that is rehealed by chalcedony and or quartz.
- moss agate - a translucent chalcedony that encloses moss-like manganese or iron oxide dendrites.
- botryoidal agate – agate that exhibits botryoidal texture. An external hummocky to rounded form similar to bunches of grapes.
- dendritic agate - moss agate that exhibits a distinct dendritic pattern.
- flame agate - a dendritic agate with red to orange flame-shaped dendrites
- iris agate – an agate that exhibits a spectral display of colors due to microscopic diffraction grating caused by alternating bands of material that has higher and lower refractive indices.
|A very attractive Montana blue agate sent to me by a collector|
|Tiger's Eye specimen - photo courtesy of Tom Nissen|
|Chalcedony colored by fuchsite mica from Copper Mountain,|
Famous Gemstones & Specimens
|Banded onyx agate enclosing geode with crystalline quartz.|
Specimen from the Jay Sundberg collection, Rawlins, WY
|This is not really a photo of some quartz, but instead it is a strategically placed ad for one of my books.|
|Discovery of a giant jasper deposit, Rattlesnake Hills, Wyoming. Jasper, jasper, jasper everywhere on Jasper Hill |
in the Rattlesnake Hills gold district. Photo shows my field assistant - Wayne Sutherland (photo by the author).
|Quartz crystal in nephrite (jade) from the Granite Mountains, Wyoming.|
|Quartz from Big Creek district, Wyoming|
|Jasper breccia from Tin Cup district, Granite Mountains, Wyoming|
|Here is an extremely rare geode! This is actually a peridotite nodule collected|
from a kimberlite in Wyoming - note the two large pyrope garnets on the side.
The center of this peridotite was dissolved and coated with tiny prismatic
|Yep, another strategically placed book ad.|