Mineralogy of the Pikes Peak Region
Encyclopedia
The Pikes Peak
region is renowned for its rare mineral specimens. It is a favorite collecting area for rock hounds and serious collectors alike. Scientists from around the world come to Colorado to study the minerals of this region. Because the granite covers a large portion of the Colorado Front Range
, there are good mineral collecting areas scattered all over the Pikes Peak region. The collecting localities range from near Colorado Springs on the south to just west of Denver on the north.
formed in several stages. In the initial stage, about 1.02 billion years ago, a large mass of magma
intruded into what is now the Front Range of Colorado. Although there may have been volcanoes overlying the intrusion, the majority of the magma never reached the surface, but formed and cooled at a depth of about 1 to 2 miles (1.6 to 3.3 km). Ultimately, the underground extent of the magma covered an area of 1200 square miles (3,108 km²). Later on, over the next 40-million years, newer pulses of magma pushed into the existing granite, re-melting and pushing it aside to form, what are now called "intrusive centers." As the magma flowed into these intrusive centers, it tended to form a circular masses of rock with concentric rings of varying composition that look something like a bulls eye. The granite in the intrusive centers is different from the original granite, with higher concentrations of rare elements and more exotic minerals. Some of the best mineral collecting areas in Colorado can be found around the edges of these intrusive centers.
When a new pulse of magma forced its way upward, the edges in contact with the older magma cooled rapidly forming a kind of "skin" of fine-grained granite. Since fine-grained granite is less porous, this "outer skin" sealed the magma body and helped to trap rare elements and water inside. Over time, the water and rare elements were concentrated along the edges of the magma.
While the magma cooled and crystallized, the water content of the remaining liquid magma increased rapidly. This is because molten magma can hold water, but the solid crystals cannot. As a result, as each crystal is formed, the water that was contained in the original molten magma is forced out of the crystal. As more crystals are formed, more water is concentrated in less and less magma.
As the water and certain elements were concentrated along the edges of the magma, even larger crystals began to form. At the same time, the water helped produce open pockets called miarolitic cavities
. The cavities are important because they allow the crystals to grow freely without interference from other crystal faces or the surrounding rock. Although good crystal occur within solid masses of rock, the most perfectly formed specimens usually come from miarolitic cavities.
Because the intrusive centers were often circular and the cooling took place from the outside in, certain minerals were concentrated in ring-shaped zones around the edges of an intrusive center. For example, in the Tarryall region, most of the topaz is found near the edges of the intrusion.
crystals and amazonite
, with topaz
, phenakite
and other rarer minerals in certain areas. Although most collecting areas have this same basic assortment of minerals, each area is distinctive and tends to feature certain minerals over others.
The collecting area, starting from the southern-most localities, include:
The collecting areas start around Helen Hunt Falls and extend south to St. Peter's Dome and to the North as far as the High Drive. In addition to the typical smokey quartz crystals and amazonite, the Gold Camp Road area contains several minerals that are relatively rare in other parts of region. The area has an abundance of fluorine minerals such as fluorite
and more rare minerals such as cryolite
, bastnäsite
and tysonite. Several localities contain the rare amphibole
riebeckite
and the even more rare mineral astrophyllite
. Finally, there are several locations where large and colorful crystals of zircon
can be found.
Like all the other Pikes Peak collecting areas, Crystal Park contains the usual smokey quartz and amazonite crystals. In addition, topaz is more abundant here than in the Gold Camp road area.
, the main hiking route to the summit of Pikes Peak. The most famous collecting area on the Peak is Glenn Cove, a glacial cirque
located at 11000 feet (3,352.8 m) on the north side of the mountain. Quartz crystals, amazonite and topaz crystals can be found in pockets on steep cliffs in this area.
Like Crystal Park, the eastern part of the Crystal Peak area is on private land and has been converted into a housing development. Nevertheless, the Western and North parts of the region are on National Forest land.
Crystal Peak is one of the most famous mineral collecting localities in Colorado. Specimens from Crystal Peak are sometimes referred to as coming form Lake George or Florissant, the actual collecting area located near Crystal Peak. The area has produced some of the finest smokey quartz and amazonite specimens in the world. It is especially noted for specimens that combine deep black smokey quartz crystal intermixed with deep blue amazonite. Other minerals such as topaz, fluorite and goethite
have been found in the area.
feldspar.
The Tarryall Mountains are famous as being one of the better topaz localities in the region. They are found in the typical pegmatite veins and pockets, but also as placer deposit
s where flowing water and gravity have sorted the slightly heaver topaz to the bottom of gravels.
Devils Head is located about 33 miles (53.1 km) south-south east of Denver on the Rampart Range Road. Like the other localities, Devils Head is another intrusive center and it forms a prominent, 9700 feet (2,956.6 m) peak whose pinnacles are easily visible from Denver.
The major collecting areas are on the west side of the mountain and they contain the usual assortment of smoky quartz and amazonite, although, like the Tarryalls, the amazonite is usually very pale and is most often grades into plain microcline.
Devils Head is most noted for large topaz crystals and even larger smokey quartz crystals. Perfect crystal of gem quality, deep black, smokey quartz, several feet in length have been found in the area.
The Rosalie Lobe contains the same minerals that are found in the intrusive centers further to the south, most notably smokey quartz, amazonite and topaz.
Pikes Peak
Pikes Peak is a mountain in the Front Range of the Rocky Mountains, west of Colorado Springs, Colorado, in El Paso County in the United States of America....
region is renowned for its rare mineral specimens. It is a favorite collecting area for rock hounds and serious collectors alike. Scientists from around the world come to Colorado to study the minerals of this region. Because the granite covers a large portion of the Colorado Front Range
Front Range
The Front Range is a mountain range of the Southern Rocky Mountains of North America located in the north-central portion of the U.S. State of Colorado and southeastern portion of the U.S. State of Wyoming. It is the first mountain range encountered moving west along the 40th parallel north across...
, there are good mineral collecting areas scattered all over the Pikes Peak region. The collecting localities range from near Colorado Springs on the south to just west of Denver on the north.
Geological history
The Pikes Peak granitePikes Peak granite
The Pikes Peak granite is a widespread geologic formation found in the central part of the Front Range of Colorado. The granite gets its name from the mountain Pikes Peak, which is made up almost entirely of the distinctive, brick-red rock...
formed in several stages. In the initial stage, about 1.02 billion years ago, a large mass of magma
Magma
Magma is a mixture of molten rock, volatiles and solids that is found beneath the surface of the Earth, and is expected to exist on other terrestrial planets. Besides molten rock, magma may also contain suspended crystals and dissolved gas and sometimes also gas bubbles. Magma often collects in...
intruded into what is now the Front Range of Colorado. Although there may have been volcanoes overlying the intrusion, the majority of the magma never reached the surface, but formed and cooled at a depth of about 1 to 2 miles (1.6 to 3.3 km). Ultimately, the underground extent of the magma covered an area of 1200 square miles (3,108 km²). Later on, over the next 40-million years, newer pulses of magma pushed into the existing granite, re-melting and pushing it aside to form, what are now called "intrusive centers." As the magma flowed into these intrusive centers, it tended to form a circular masses of rock with concentric rings of varying composition that look something like a bulls eye. The granite in the intrusive centers is different from the original granite, with higher concentrations of rare elements and more exotic minerals. Some of the best mineral collecting areas in Colorado can be found around the edges of these intrusive centers.
When a new pulse of magma forced its way upward, the edges in contact with the older magma cooled rapidly forming a kind of "skin" of fine-grained granite. Since fine-grained granite is less porous, this "outer skin" sealed the magma body and helped to trap rare elements and water inside. Over time, the water and rare elements were concentrated along the edges of the magma.
While the magma cooled and crystallized, the water content of the remaining liquid magma increased rapidly. This is because molten magma can hold water, but the solid crystals cannot. As a result, as each crystal is formed, the water that was contained in the original molten magma is forced out of the crystal. As more crystals are formed, more water is concentrated in less and less magma.
As the water and certain elements were concentrated along the edges of the magma, even larger crystals began to form. At the same time, the water helped produce open pockets called miarolitic cavities
Miarolitic cavities
Miarolitic cavities are typically crystal lined irregular cavities or vugs most commonly found in granitic pegmatites, but also found in a variety of igneous rocks. The central portions of pegmatites are often miarolitic as the pegmatite dike crystallizes from the outside walls toward the center...
. The cavities are important because they allow the crystals to grow freely without interference from other crystal faces or the surrounding rock. Although good crystal occur within solid masses of rock, the most perfectly formed specimens usually come from miarolitic cavities.
Because the intrusive centers were often circular and the cooling took place from the outside in, certain minerals were concentrated in ring-shaped zones around the edges of an intrusive center. For example, in the Tarryall region, most of the topaz is found near the edges of the intrusion.
Collecting areas
There are seven major collecting areas within the Pikes Peak granite. All of the collecting areas have the same basic assemblage minerals, predominately consisting of smokey quartzQuartz
Quartz is the second-most-abundant mineral in the Earth's continental crust, after feldspar. It is made up of a continuous framework of SiO4 silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall formula SiO2. There are many different varieties of quartz,...
crystals and amazonite
Amazonite
Amazonite is a green variety of microcline feldspar.The name is taken from that of the Amazon River, from which certain green stones were formerly obtained, but it is doubtful whether green feldspar occurs in the Amazon area.Amazonite is a mineral of limited occurrence...
, with topaz
Topaz
Topaz is a silicate mineral of aluminium and fluorine with the chemical formula Al2SiO42. Topaz crystallizes in the orthorhombic system and its crystals are mostly prismatic terminated by pyramidal and other faces.-Color and varieties:...
, phenakite
Phenakite
Phenakite or phenacite is a fairly rare nesosilicate mineral consisting of beryllium orthosilicate, Be2SiO4. Occasionally used as a gemstone, phenakite occurs as isolated crystals, which are rhombohedral with parallel-faced hemihedrism, and are either lenticular or prismatic in habit: the...
and other rarer minerals in certain areas. Although most collecting areas have this same basic assortment of minerals, each area is distinctive and tends to feature certain minerals over others.
The collecting area, starting from the southern-most localities, include:
Gold Camp Road
The Gold Camp Road is old railroad grade that runs from Colorado Springs to Cripple Creek. It was one of the three railroads that served the Cripple Creek Mining District at the turn of the 20th Century. It can be reached from Colorado Springs by driving up North Cheyenne Canyon.The collecting areas start around Helen Hunt Falls and extend south to St. Peter's Dome and to the North as far as the High Drive. In addition to the typical smokey quartz crystals and amazonite, the Gold Camp Road area contains several minerals that are relatively rare in other parts of region. The area has an abundance of fluorine minerals such as fluorite
Fluorite
Fluorite is a halide mineral composed of calcium fluoride, CaF2. It is an isometric mineral with a cubic habit, though octahedral and more complex isometric forms are not uncommon...
and more rare minerals such as cryolite
Cryolite
Cryolite is an uncommon mineral identified with the once large deposit at Ivigtût on the west coast of Greenland, depleted by 1987....
, bastnäsite
Bastnasite
The mineral bastnäsite is one of a family of three carbonate-fluoride minerals, which includes bastnäsite- with a formula of CO3F, bastnäsite- with a formula of CO3F, and bastnäsite- with a formula of CO3F. Most bastnäsite is bastnäsite-, and cerium is by far the most common of the rare earths in...
and tysonite. Several localities contain the rare amphibole
Amphibole
Amphibole is the name of an important group of generally dark-colored rock-forming inosilicate minerals, composed of double chain tetrahedra, linked at the vertices and generally containing ions of iron and/or magnesium in their structures.-Mineralogy:...
riebeckite
Riebeckite
Riebeckite is a sodium-rich member of the amphibole group of silicate minerals, chemical formula [][Na2][32][2|Si8O22]. It forms a series with magnesioriebeckite. It crystallizes in the monoclinic system, usually as long prismatic crystals showing a diamond-shaped cross section, but also in...
and the even more rare mineral astrophyllite
Astrophyllite
Astrophyllite is a very rare, brown to golden-yellow hydrous potassium iron titanium silicate mineral. Belonging to the astrophyllite group, astrophyllite may be classed either as an inosilicate, phyllosilicate, or an intermediate between the two. It forms an isomorphous series with kupletskite, to...
. Finally, there are several locations where large and colorful crystals of zircon
Zircon
Zircon is a mineral belonging to the group of nesosilicates. Its chemical name is zirconium silicate and its corresponding chemical formula is ZrSiO4. A common empirical formula showing some of the range of substitution in zircon is 1–x4x–y...
can be found.
Crystal Park
To the north is Crystal Park. Crystal Park is situated on the eastern slope of Camerons Cone, a 10700 feet (3,261.4 m) conical peak southeast of the summit of Pikes Peak. Just to the east of Camerons Cone, the mountains form a protected, bowl-shaped valley called Crystal Park. It can be reached by a well maintained automobile road from Manitou Springs and by several trails from the southeast and east. Currently much of the park is a private home development. The collecting area ranges from the Northern slopes of Camerons Cone to Specimen Rock on the south. Much of this area is National Forest.Like all the other Pikes Peak collecting areas, Crystal Park contains the usual smokey quartz and amazonite crystals. In addition, topaz is more abundant here than in the Gold Camp road area.
Pikes Peak
Pikes Peak is itself, an intrusive center and smokey quartz and amazonite can be found in many areas within four miles (6 km) of the summit. For example, amazonite can be found next to Barr TrailBarr Trail
Barr Trail is a popular trail that climbs from Manitou Springs, Colorado, USA to the top of Pikes Peak. The trail is rated more difficult because of its long sustained grade rising to an especially high elevation...
, the main hiking route to the summit of Pikes Peak. The most famous collecting area on the Peak is Glenn Cove, a glacial cirque
Cirque
Cirque may refer to:* Cirque, a geological formation* Makhtesh, an erosional landform found in the Negev desert of Israel and Sinai of Egypt*Cirque , an album by Biosphere* Cirque Corporation, a company that makes touchpads...
located at 11000 feet (3,352.8 m) on the north side of the mountain. Quartz crystals, amazonite and topaz crystals can be found in pockets on steep cliffs in this area.
Crystal Peak
Crystal Peak is located about 35 miles (56.3 km) west of Colorado Springs on Highway 24. It is north of the highway and between Florissant and Lake George. Crystal Peak itself is a distinctive, conical knoll about 3.5 miles (5.6 km) due north of Florissant. Geologically, it is also an intrusive center and the geological maps show a very characteristic ring-shaped structure about 5 miles (8 km) in diameter.Like Crystal Park, the eastern part of the Crystal Peak area is on private land and has been converted into a housing development. Nevertheless, the Western and North parts of the region are on National Forest land.
Crystal Peak is one of the most famous mineral collecting localities in Colorado. Specimens from Crystal Peak are sometimes referred to as coming form Lake George or Florissant, the actual collecting area located near Crystal Peak. The area has produced some of the finest smokey quartz and amazonite specimens in the world. It is especially noted for specimens that combine deep black smokey quartz crystal intermixed with deep blue amazonite. Other minerals such as topaz, fluorite and goethite
Goethite
Goethite , named after the German polymath Johann Wolfgang von Goethe, is an iron bearing oxide mineral found in soil and other low-temperature environments. Goethite has been well known since prehistoric times for its use as a pigment. Evidence has been found of its use in paint pigment samples...
have been found in the area.
Tarryall Mountains
The Tarryall Mountains are located about 12 miles (19.3 km) north of Lake George. They represent an intrusive center called the Redskin Stock. Like the other localities in the region, smokey quartz and amazonite are the primary minerals, however, the amazonite is usually very pale and more commonly ordinary microclineMicrocline
Microcline is an important igneous rock-forming tectosilicate mineral. It is a potassium-rich alkali feldspar. Microcline typically contains minor amounts of sodium. It is common in granite and pegmatites. Microcline forms during slow cooling of orthoclase; it is more stable at lower temperatures...
feldspar.
The Tarryall Mountains are famous as being one of the better topaz localities in the region. They are found in the typical pegmatite veins and pockets, but also as placer deposit
Placer deposit
In geology, a placer deposit or placer is an accumulation of valuable minerals formed by gravity separation during sedimentary processes. The name is from the Spanish word placer, meaning "alluvial sand". Placer mining is an important source of gold, and was the main technique used in the early...
s where flowing water and gravity have sorted the slightly heaver topaz to the bottom of gravels.
Devils Head
The major collecting areas are on the west side of the mountain and they contain the usual assortment of smoky quartz and amazonite, although, like the Tarryalls, the amazonite is usually very pale and is most often grades into plain microcline.
Devils Head is most noted for large topaz crystals and even larger smokey quartz crystals. Perfect crystal of gem quality, deep black, smokey quartz, several feet in length have been found in the area.
Rosalie Lobe
The Rosalie Lobe is located on the southeast slope of Mount Evans the prominent 14000 feet (4,267.2 m) peak just west of Denver. The Rosalie Lobe is interesting because it is an isolated lobe of the Pike Peak Granite, separated by five miles from the main body of the intrusion. It is accessible from Highway 285 from the town Harris Park which is about 30 miles (48.3 km) southwest of Denver.The Rosalie Lobe contains the same minerals that are found in the intrusive centers further to the south, most notably smokey quartz, amazonite and topaz.