Conway granite is a typically pink (or mesoperthitic)

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 alumino ...

granite Granite () is a coarse-grained (phaneritic) 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 cools and solidifies undergro ...

."Conway Granite." Mineral Resources On-Line Spatial Data. U.S. Geological Survey. U.S. Department of the Interior. No date.
Accessed 2011-03-30. It is

amphibole Amphibole () is a group of inosilicate minerals, forming prism or needlelike crystals, composed of double chain tetrahedra, linked at the vertices and generally containing ions of iron and/or magnesium in their structures. Its IMA symbol is A ...

-free and of coarse

particle size Particle size is a notion introduced for comparing dimensions of solid particles ('' flecks''), liquid particles ('' droplets''), or gaseous particles ('' bubbles''). The notion of particle size applies to particles in colloids, in ecology, in ...

(with portions of the rock fine-grained or

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 all ...

). Conway granite has a relatively high concentration of

thorium Thorium is a weakly radioactive metallic chemical element with the symbol Th and atomic number 90. Thorium is silvery and tarnishes black when it is exposed to air, forming thorium dioxide; it is moderately soft and malleable and has a high me ...

, at about 56 (±6) ppm; this amount is not enough to make the granite dangerously radioactive, but it is sufficient to make the rock a low-grade (almost certainly not economic, at least in the early years) source of thorium for a

thorium fuel cycle The thorium fuel cycle is a nuclear fuel cycle that uses an isotope of thorium, , as the fertile material. In the reactor, is transmuted into the fissile artificial uranium isotope which is the nuclear fuel. Unlike natural uranium, natural tho ...

. Geologist

Edward Hitchcock Edward Hitchcock (May 24, 1793 – February 27, 1864) was an American geologist and the third President of Amherst College (1845–1854). Life Born to poor parents, he attended newly founded Deerfield Academy, where he was later principal, ...

named the granite in 1877 after the town of

Conway, New Hampshire Conway is a town in Carroll County, New Hampshire, United States. It is the most populous community in the county, with a population of 9,822 at the 2020 census, down from 10,115 at the 2010 census. The town is on the southeastern edge of the Whi ...

, which is near where it is mined. The

Old Man of the Mountain The Old Man of the Mountain, also called the Great Stone Face and the Profile, was a series of five granite cliff ledges on Cannon Mountain in Franconia, New Hampshire, United States, that appeared to be the jagged profile of a human face when ...

, a famous geologic feature in

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

, was made of Conway granite. (The rock formation collapsed in 2003.) Conway granite is found throughout the lower areas of the central White Mountains, such as

Franconia Notch Franconia Notch (elev. ) is a major mountain pass through the White Mountains of New Hampshire. Dominated by Cannon Mountain to the west and Mount Lafayette to the east, it lies principally within Franconia Notch State Park and is traversed by ...

Crawford Notch Crawford Notch is a major pass through the White Mountains of New Hampshire, located in Hart's Location. Roughly half of that town is contained in Crawford Notch State Park. The high point of the notch, at approximately above sea level, is at ...

, the center of the

Pemigewasset Wilderness The Pemigewasset Wilderness is a federally designated Wilderness Area in the heart of New Hampshire's White Mountains. It is a part of the White Mountain National Forest. It is New Hampshire's largest wilderness area. The Wilderness Area consi ...

, and the

Saco River The Saco River (Abenaki language, Abenaki: ''Sαkóhki'') is a river in northeastern New Hampshire and southwestern Maine in the United States. It drains a rural area of of forests and farmlands west and southwest of Portland, Maine, Portland ...

valley. Other exposures of the formation include the Belknap Mountains south of

Lake Winnipesaukee Lake Winnipesaukee () is the largest lake in the U.S. state of New Hampshire, located in the Lakes Region at the foothills of the White Mountains. It is approximately long (northwest-southeast) and from wide (northeast-southwest), covering & ...

References

Granite Igneous petrology of New Hampshire {{Petrology-stub