Pikes Peak granite
Encyclopedia
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 14110 feet (4,300.7 m) mountain Pikes Peak
, which is made up almost entirely of the distinctive, brick-red rock. Pikes Peak itself is only a small part of a much larger formation known as the Pikes Peak batholith
.
formed under what is now central Colorado. Some of this magma worked its way to the surface and formed volcanoes similar to what we might see today in Washington and Oregon
.
After the volcanic activity died away, a large mass of molten magma was left underground. Because the magma was buried about 2 miles (5 km) underground, it took thousands of years for it to cool and this created the granite
that we now see on the slopes of Pikes Peak and other areas of the Front Range.
Over the next billion years, the now cooled granite was gradually exposed through erosion
of overlying rocks. About 60 million years ago, parts of the Western U.S. were subjected to a series of uplifts, known as the Laramide orogeny
, that eventually formed the modern Rocky Mountains
and raised Pikes Peak to its current height. Pikes Peak, like other portions of Colorado Rockies is still being uplifted today as a part of larger tectonic processes effecting the Western United States.
Today, the Pikes Peak Batholith and Granite is exposed over a large part of the central Front Range of Colorado. It is found as far north as the southern slopes of Mount Evans
west of Denver
, west to South Park
, and as far south as Cañon City
. The batholith is about 80 miles (130 km) long in the north-south direction and about 25 miles (40 km) wide east to west. Even more of it remains hidden underground. Geologists have found the granite at the bottom of deep wells on the plains and magnetic sensors have detected it as much as 80 miles (128.7 km) to the east.
feldspar
and various iron minerals that permeate the rock. The long cooling time and the chemical composition of the original magma allowed large crystals to precipitate out of the magma. As a result, in many places the granite is very coarse grained, made up almost entirely of large crystals of feldspar, typically about a centimeter across. This makes the granite easily weathered and very crumbly. Almost every hill and slope in the Pikes Peak region is covered with thick blankets of loose gravel (scree
) made up of marble-sized grains of feldspar.
In some places, the cooling process lasted long enough to form pegmatites that contain large, pure crystals of various minerals. The chemistry of the cooling magma produced a complex and unique mineralogy
that attracts collectors from around the world and the Pikes Peak region is famous for its spectacular mineral specimens.
Smoky quartz
crystals and topaz
are found in many places in the Pikes Peak granite. Probably the most famous mineral from the area is amazonite
, a bluish form of microcline feldspar that is relatively rare in other parts of the world. Many museum collections have stunning specimens of deep blue amazonite crystals studded with jet-black smoky quartz crystals.
Geologic formation
A formation or geological formation is the fundamental unit of lithostratigraphy. A formation consists of a certain number of rock strata that have a comparable lithology, facies or other similar properties...
found in the central part of the 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...
of Colorado
Colorado
Colorado is a U.S. state that encompasses much of the Rocky Mountains as well as the northeastern portion of the Colorado Plateau and the western edge of the Great Plains...
. The granite gets its name from the 14110 feet (4,300.7 m) mountain Pikes Peak
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....
, which is made up almost entirely of the distinctive, brick-red rock. Pikes Peak itself is only a small part of a much larger formation known as the Pikes Peak batholith
Batholith
A batholith is a large emplacement of igneous intrusive rock that forms from cooled magma deep in the Earth's crust...
.
Origin
About 1.08 billion years ago, a large pool of magmaMagma
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...
formed under what is now central Colorado. Some of this magma worked its way to the surface and formed volcanoes similar to what we might see today in Washington and Oregon
Cascade Range
The Cascade Range is a major mountain range of western North America, extending from southern British Columbia through Washington and Oregon to Northern California. It includes both non-volcanic mountains, such as the North Cascades, and the notable volcanoes known as the High Cascades...
.
After the volcanic activity died away, a large mass of molten magma was left underground. Because the magma was buried about 2 miles (5 km) underground, it took thousands of years for it to cool and this created the granite
Granite
Granite is a common and widely occurring type of intrusive, felsic, igneous rock. Granite usually has a medium- to coarse-grained texture. Occasionally some individual crystals are larger than the groundmass, in which case the texture is known as porphyritic. A granitic rock with a porphyritic...
that we now see on the slopes of Pikes Peak and other areas of the Front Range.
Erosion
Erosion
Erosion is when materials are removed from the surface and changed into something else. It only works by hydraulic actions and transport of solids in the natural environment, and leads to the deposition of these materials elsewhere...
of overlying rocks. About 60 million years ago, parts of the Western U.S. were subjected to a series of uplifts, known as the Laramide orogeny
Laramide orogeny
The Laramide orogeny was a period of mountain building in western North America, which started in the Late Cretaceous, 70 to 80 million years ago, and ended 35 to 55 million years ago. The exact duration and ages of beginning and end of the orogeny are in dispute, as is the cause. The Laramide...
, that eventually formed the modern Rocky Mountains
Rocky Mountains
The Rocky Mountains are a major mountain range in western North America. The Rocky Mountains stretch more than from the northernmost part of British Columbia, in western Canada, to New Mexico, in the southwestern United States...
and raised Pikes Peak to its current height. Pikes Peak, like other portions of Colorado Rockies is still being uplifted today as a part of larger tectonic processes effecting the Western United States.
Today, the Pikes Peak Batholith and Granite is exposed over a large part of the central Front Range of Colorado. It is found as far north as the southern slopes of Mount Evans
Mount Evans
Mount Evans is a mountain in the Front Range region of the Rocky Mountains, in Clear Creek County, Colorado. It is one of 54 fourteeners in Colorado, and the closest fourteener to Denver...
west of Denver
Denver, Colorado
The City and County of Denver is the capital and the most populous city of the U.S. state of Colorado. Denver is a consolidated city-county, located in the South Platte River Valley on the western edge of the High Plains just east of the Front Range of the Rocky Mountains...
, west to South Park
South Park (Colorado basin)
South Park is a high intermontane grassland basin, approximately 10,000 ft in elevation, in the Rocky Mountains of central Colorado. It encompasses approximately 1,000 square miles around the headwaters of the South Platte River in Park County approximately 60 mi southwest of Denver...
, and as far south as Cañon City
Cañon City, Colorado
The City of Cañon City is a Home Rule Municipality that is the county seat and the most populous city of Fremont County, State of Colorado. The United States Census Bureau estimated that the city population was 16,000 in 2005. Cañon City is noted for being the location of nine state and four ...
. The batholith is about 80 miles (130 km) long in the north-south direction and about 25 miles (40 km) wide east to west. Even more of it remains hidden underground. Geologists have found the granite at the bottom of deep wells on the plains and magnetic sensors have detected it as much as 80 miles (128.7 km) to the east.
Mineralogy
The granite ranges in color from light pink to almost red. The pink color is due to large amounts of 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
Feldspar
Feldspars are a group of rock-forming tectosilicate minerals which make up as much as 60% of the Earth's crust....
and various iron minerals that permeate the rock. The long cooling time and the chemical composition of the original magma allowed large crystals to precipitate out of the magma. As a result, in many places the granite is very coarse grained, made up almost entirely of large crystals of feldspar, typically about a centimeter across. This makes the granite easily weathered and very crumbly. Almost every hill and slope in the Pikes Peak region is covered with thick blankets of loose gravel (scree
Scree
Scree, also called talus, is a term given to an accumulation of broken rock fragments at the base of crags, mountain cliffs, or valley shoulders. Landforms associated with these materials are sometimes called scree slopes or talus piles...
) made up of marble-sized grains of feldspar.
In some places, the cooling process lasted long enough to form pegmatites that contain large, pure crystals of various minerals. The chemistry of the cooling magma produced a complex and unique mineralogy
Mineralogy of the Pikes Peak Region
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...
that attracts collectors from around the world and the Pikes Peak region is famous for its spectacular mineral specimens.
Smoky quartz
Quartz
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 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:...
are found in many places in the Pikes Peak granite. Probably the most famous mineral from the area is 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...
, a bluish form of microcline feldspar that is relatively rare in other parts of the world. Many museum collections have stunning specimens of deep blue amazonite crystals studded with jet-black smoky quartz crystals.