Quartz monzonite is an intrusive,

felsic In geology, felsic is a grammatical modifier, modifier describing igneous rocks that are relatively rich in elements that form feldspar and quartz.Marshak, Stephen, 2009, ''Essentials of Geology,'' W. W. Norton & Company, 3rd ed. It is contrasted ...

igneous rock Igneous rock ( ), or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rocks are formed through the cooling and solidification of magma or lava. The magma can be derived from partial ...

that has an approximately equal proportion of

orthoclase Orthoclase, or orthoclase feldspar ( endmember formula K Al Si3 O8), is an important tectosilicate mineral which forms igneous rock. The name is from the Ancient Greek for "straight fracture", because its two cleavage planes are at right angles ...

and

plagioclase Plagioclase ( ) is a series of Silicate minerals#Tectosilicates, tectosilicate (framework silicate) minerals within the feldspar group. Rather than referring to a particular mineral with a specific chemical composition, plagioclase is a continu ...

feldspar Feldspar ( ; sometimes spelled felspar) is a group of rock-forming aluminium tectosilicate minerals, also containing other cations such as sodium, calcium, potassium, or barium. The most common members of the feldspar group are the ''plagiocl ...

s. It is typically a light colored phaneritic (coarse-grained) to

porphyritic Porphyritic is an adjective used in geology to describe igneous rocks with a distinct difference in the size of mineral crystals, with the larger crystals known as phenocrysts. Both extrusive and intrusive rocks can be porphyritic, meaning ...

granitic rock. The plagioclase is typically intermediate to sodic in composition, andesine to oligoclase.

Quartz Quartz is a hard, crystalline mineral composed of silica (silicon dioxide). The Atom, atoms are linked in a continuous framework of SiO4 silicon–oxygen Tetrahedral molecular geometry, tetrahedra, with each oxygen being shared between two tet ...

is present in significant amounts.

Biotite Biotite is a common group of phyllosilicate minerals within the mica group, with the approximate chemical formula . It is primarily a solid-solution series between the iron- endmember annite, and the magnesium-endmember phlogopite; more al ...

and/or

hornblende Hornblende is a complex silicate minerals#Inosilicates, inosilicate series of minerals. It is not a recognized mineral in its own right, but the name is used as a general or field term, to refer to a dark amphibole. Hornblende minerals are common ...

constitute the dark minerals. Because of its coloring, it is often confused with

granite Granite ( ) is a coarse-grained (phanerite, phaneritic) intrusive rock, intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase. It forms from magma with a high content of silica and alkali metal oxides that slowly coo ...

, but whereas granite contains more than 20% quartz, quartz monzonite is only 5–20% quartz. Rock with less than five percent quartz is classified as

monzonite Monzonite is an igneous intrusive rock, formed by slow cooling of underground magma that has a moderate silica content and is enriched in alkali metal oxides. Monzonite is composed mostly of plagioclase and alkali feldspar. Syenodiorite is an ...

. A rock with more alkali feldspar is a syenite whereas one with more plagioclase is a quartz diorite.Classification of Igneous Rocks
The fine grained

volcanic rock Volcanic rocks (often shortened to volcanics in scientific contexts) are rocks formed from lava erupted from a volcano. Like all rock types, the concept of volcanic rock is artificial, and in nature volcanic rocks grade into hypabyssal and me ...

equivalent of quartz monzonite is quartz latite. The term adamellite was originally applied by A. Cathrein in 1890 to orthoclase-bearing tonalite (likely a

granodiorite Granodiorite ( ) is a coarse-grained (phaneritic) intrusive igneous rock similar to granite, but containing more plagioclase feldspar than orthoclase feldspar. The term banatite is sometimes used informally for various rocks ranging from gra ...

) at Monte Adamello, Italy, in 1890, but later came to refer to quartz monzonite. The term is now deprecated. Quartz monzonite porphyry is often associated with

copper Copper is a chemical element; it has symbol Cu (from Latin ) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkish-orang ...

mineralization in the

porphyry copper Porphyry copper deposits are copper ore bodies that are formed from hydrothermal circulation, hydrothermal fluids that originate from a voluminous magma chamber several kilometers below the deposit itself. Predating or associated with those flui ...

ore deposits.

Geographic distribution

United States

In the White Mountains and western highlands of

New Hampshire New Hampshire ( ) is a U.S. state, state in the New England region of the Northeastern United States. It borders Massachusetts to the south, Vermont to the west, Maine and the Gulf of Maine to the east, and the Canadian province of Quebec t ...

, the Kinsman Quartz Monzonite is an extensive formation that underlies Kinsman Mountain, parts of Franconia Notch, Mount Cardigan, and Mount Sunapee. Stone Mountain in

Georgia Georgia most commonly refers to: * Georgia (country), a country in the South Caucasus * Georgia (U.S. state), a state in the southeastern United States Georgia may also refer to: People and fictional characters * Georgia (name), a list of pe ...

is a large quartz monzonite

monadnock An inselberg or monadnock ( ) is an isolated rock hill, knob, ridge, or small mountain that rises abruptly from a gently sloping or virtually level surrounding plain. In Southern Africa, a similar formation of granite is known as a koppie, an ...

. Quartz monzonite extracted from a quarry in Little Cottonwood Canyon was used to build several buildings in

Salt Lake City Salt Lake City, often shortened to Salt Lake or SLC, is the capital and most populous city of the U.S. state of Utah. It is the county seat of Salt Lake County, the most populous county in the state. The city is the core of the Salt Lake Ci ...

Utah Utah is a landlocked state in the Mountain states, Mountain West subregion of the Western United States. It is one of the Four Corners states, sharing a border with Arizona, Colorado, and New Mexico. It also borders Wyoming to the northea ...

, including

the Church of Jesus Christ of Latter-day Saints The Church of Jesus Christ of Latter-day Saints, informally known as the LDS Church or Mormon Church, is a Nontrinitarianism, nontrinitarian Restorationism, restorationist Christianity, Christian Christian denomination, denomination and the ...

Salt Lake Temple The Salt Lake Temple is a Temple (LDS Church), temple of the Church of Jesus Christ of Latter-day Saints on Temple Square in Salt Lake City, Utah, United States. At , it is the Comparison of temples of The Church of Jesus Christ of Latter-day Sa ...

, Church Administration Building, and Conference Center, as well as the Utah State Capitol. The large boulders of

Joshua Tree National Park Joshua Tree National Park is a List of national parks of the United States, US National Park located in southeastern California, straddling north-central Riverside County, California, Riverside County and part of southern San Bernardino County, ...

in southern California are quartz monzonite. A large pluton in the Atlanta lobe of the

Idaho Batholith The Idaho Batholith is a granitic and granodioritic batholith of Cretaceous- Paleogene age that covers approximately of central Idaho and adjacent Montana. The batholith has two lobes that are separate from each other geographically and ge ...

, near McCall,

Idaho Idaho ( ) is a landlocked U.S. state, state in the Pacific Northwest and Mountain states, Mountain West subregions of the Western United States. It borders Montana and Wyoming to the east, Nevada and Utah to the south, and Washington (state), ...

, is made of quartz monzonite.Idaho Batholith
/ref> The Guilford Quartz Monzonite and Woodstock Quartz Monzonite, probably comagmatic, are located in central

Maryland Maryland ( ) is a U.S. state, state in the Mid-Atlantic (United States), Mid-Atlantic region of the United States. It borders the states of Virginia to its south, West Virginia to its west, Pennsylvania to its north, and Delaware to its east ...

Australia

Queensland Queensland ( , commonly abbreviated as Qld) is a States and territories of Australia, state in northeastern Australia, and is the second-largest and third-most populous state in Australia. It is bordered by the Northern Territory, South Austr ...

, Castle Hill, Mount Stuart and Mount Louisa around

Townsville The City of Townsville is a city on the north-eastern coast of Queensland, Australia. With a population of 201,313 as of 2024, it is the largest settlement in North Queensland and Northern Australia (specifically, the parts of Australia north of ...

represent a large quartz monzonite province.

References

External links

* {{Rock type Igneous petrology Granitic rocks