| Minerals found in the Rocky Mountain region |
In order to understand minerals and gems, a background in the discipline is important (www.emporia.edu/earthsci/amber/go336/known.htm). Mineralogy is a subfield of the goesciences that includes crystallography and mineral genesis, as well as the physical, chemical, and optical properties of naturally occuring, crystalline solids (Aber, 2007). There are more than 4000 different mineral species named and more continue to be discovered.
Minerals are defined as naturally occurring, homogeneous, solid, and usually inorganic origin; all minerals possess a definite chemical composition and crystalline or atomic structure. Now that you have a background in mineralogy, read on about some of my favorites from the Rocky Mountain region west of Kansas.
Amethyst is purple variety of quartz. The color may range from light to deep purple. This purple color is caused by impurities of iron and manganese trace elements in the silicon dioxide structure. Quartz has a hardness of 7, has a vitreous luster. The fracture is commonly conchoidal and tenacity, brittle. It is a popular mineral speciment and desirable gemstone because of the beautiful color and relatively inexpensive price.
Aquamarine is a gem quality, blue green variety of beryl. It has a hardness of 7.5 - 8 and vitreous luster. The tenacity is brittle and it occurs in a hexagonal prism form. Beryl varieties are named based on color. Emerald is green to dark green beryl and aquamarine is light to dark blue or blue-green beryl. A pink to light purple beryl is known as morganite, whereas golden yellow beryl maybe called golden beryl or heliodor, which can be brown in addition to yellow. Goshenite is beryl in its purest state, colorless to white and bixbite is the red to srawberry red beryl that comes from one location in Utah. Peach or pink beryl maybe referred to as peach beryl and green beryl not colored by chromium is merely called green beryl.
Rhodochrosite comes from the Greek words ‘rhodon’ meaning rose, and ‘chroma’ meaning color. Other nicknames for the mineral are Manganese Spar, Raspberry Spar and Inca Rose. Rhodochrosite is most commonly found in shades of red, pinkish red or rose red, but can be found in a yellowish grey and brown colors because it is isomorphic with other carbonates such as siderate and calcite. The red or pink color may darken when exposed to air, and it can appear anywhere from transparent to translucent. Depending on the habit and diaphaneity, rhodochrosite can have a vitreous to pearl luster. The hardness is 3.5 to 4, and it tends to have a brittle tenacity.
The image above and right is transparent red rhodochrosite from the Sweet Home Mine, Alma, Colorado. The image was taken from Colorado Rockhounding,
http://www.peaktopeak.com/colorado/index.php3, or Mineral Gallery, www.themineralgallery.com/rhodoroom.htm.
The chemical name and group for rhodochrosite is a manganese carbonate. Although the a mineral chemical composition is definite, it may have substitutions of the following elements for Mn: Fe, Mg, Ca, Zn, & Co. Thus, with substitution comes different color possibilities. Rhodochrosite is hexagonal, and crystals often display a form showing the rhombohedral or trigonal crystal system. Rhodochrosite can occur as a hexagonal scalenohedron and it is capable of ‘twinning’.
Varieties of MnCO3 include, kutnahorite, a calcium rich variety; mangansideritean, an iron rich variety; rosinca, a banded stalactitic variety from Central America; and capillitite, a yellow and grey banded variety also from Central America.
Rhodochrosite is used as a gem stone and also as ore for manganese. It is mined domestically in several sites in Colorado and Montana. It is also mined in Germany, South Africa, Mexico, Peru and Argentina. Banded rhodochrosite is found in the abandoned silver mines of the ancient Inca civilization, where it was discovered growing as stalagmites and stalagtites.
Topaz was named for the location in which it was discovered, the Topasos Island in the Red Sea. Topaz is a widely used gemstone due to its vitreous luster and transparency. It has a hardness of 8 making it a durable and desirable stone for jewelry. Color of topaz range from colorless to yellow to pale blue; pink or red are less common.
The chemical composition of topaz is AlSiO4(OH)2. Topaz is in the orthorhombic crystal system. The average specific gravity of topaz is 3.55, and it has a brittle tenacity and uneven fracture.
Calcite is one of the most common and widely used minerals today. The name comes from the Latin word calx, meaning lime. Its chemical name is calcium carbonate and the formula is CaCO3. Calcite is part of the carbonate group. It contains 40% calcium, 12% carbon & 48% oxygen.
Calcite can be transparent, translucent or opaque. It can be colorless, white, pink, yellow or even brown in color. It is generally flourescent, and those varieties that are not, usually become flourescent after being heated. Specimens from different areas will flouresce different colors, and some are phosphorescent.
Some varieties in the calcite group include a phrite, cobalt calcite, corn spar, dogtooth calcite, hog-toothed calcite, Icelandic spar, nail-head spar, rice grain spar, salmon calcite, and sand calcite. Limestone, marble and chalk are all rocks formed from calcite.
Image to the right is a stamp issued by Iceland. The image was taken from giantcrystals.strahlen.org/europe/helgustadir.htm, the giant crystal project site.
Even after an area is determined to be safe and with minerals available for collecting, it may be illegal unless it is Bureau of Mines land. It is important to remember that many sites maybe privately owned or have filed mineral claims to them. Different states will have different regulations on collecting specimens. For more information vistit a site for laws and regulations; for example, for Utah visit http://geology.utah.gov/online/pdf/pi-23.pdf.
Possible collecting locations can be found at
Fine specimens of minerals and gems are still free for the taking if you know what to look for and where to look. If you are planning a trip or vacation to the Rocky Mountains, why not do a little research and see what you could "dig up" while your there! A trip to Cripple Creek, Colorado can be topped off with a tour of an old gold mine. Colorado and Utah collecting sites are near public camping grounds. For more information on finding minerals throughout the United States a new program on the Travel Channel is not only fun to watch, but can give you great ideas for your next vacation! Find Cash and Treasures at travel.discovery.com/tv/tv-shows.html.
Return to the GO 336 Student Webpages, www.emporia.edu/earthsci/amber/go336/webpages.htm.
Webpage created fall semester 2007; last update Decemer 21, 2007.
Common Minerals Mined in the Rockies
Collection Areas
-- Each year hundreds of people are killed or seriously injured exploring abandon mines in the United States. Abandoned mines are common throughout the Rocky Mountains and if you come upon one DO NOT ATTEMPT TO ENTER IT! Among the undetectable hazards in mines is the presence of toxic gases and danger of cave-ins. For more information on abandon mine dangers go to mining.state.co.us/Abandoned%20Mines.htm at the Colorado Division of Reclamation Mining & Safety.
Conclusion
Related Links
Colorado Division of Reclaimation--Mining and Safety
http://mining.state.co.us/Tourist%20Mines.htm
Colorado Rockhounding
http://www.peaktopeak.com/colorado/index.php3
Topaz Mountain Collecting at the Denver Mineral Show
www.greatbasinminerals.com/Collecting%20Reports/
Sept%202006%20Topaz%20Mtn/Colorado%20Topaz%20Trip,
%20Sept,%202006.htm>
