The Highwood Mountains cover approximately 4,659 km² (1,799 sq mi) in north central Montana

Montana

Montana is a state in the Western United States. The western third of Montana contains numerous mountain ranges. Smaller, "island ranges" are found in the central third of the state, for a total of 77 named ranges of the Rocky Mountains. This geographical fact is reflected in the state's name,...

 in the U.S.

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

, east of Great Falls

Great Falls, Montana

Great Falls is a city in and the county seat of Cascade County, Montana, United States. The population was 58,505 at the 2010 census. It is the principal city of the Great Falls, Montana Metropolitan Statistical Area, which encompasses all of Cascade County...

 and Benton Lake National Wildlife Refuge

Benton Lake National Wildlife Refuge

Benton Lake National Wildlife Refuge is located in the central portions of the U.S. state of Montana. It lies in northern Cascade County, just north of the city of Great Falls. It is part of the larger Benton Lake National Wildlife Refuge Complex, which includes the Lost Trail National Wildlife...

, at the northern end of the Lewis and Clark National Forest

Lewis and Clark National Forest

Lewis and Clark National Forest is located in west central Montana, United States. Spanning , the forest is managed as two separate zones. The eastern sections, under the Jefferson Division, is a mixture of grass and shrublands dotted with "island" pockets of forested areas. Here, cattle leases to...

. http://www.fs.fed.us/r1/lewisclark/images/vicmap.GIF The mountains were included in Highwood Mountains National Forest

Highwood Mountains National Forest

Highwood Mountains National Forest was established as the Highwood Mountains Forest Reserve by the U.S. Forest Service in Montana on April 12, 1906 with . It became a National Forest on March 4, 1907...

 until 1908, when the unit became part of Lewis and Clark National Forest.

Nearby are Highwood, Montana

Highwood, Montana

Highwood is a census-designated place in Chouteau County, Montana, United States. The population was 189 at the 2000 census. It first had a post office opened in 1881. It was closed and reopened a few times until 1886 after which it has remained open continuously.-Geography:Highwood is located at...

 and the Missouri River

Missouri River

The Missouri River flows through the central United States, and is a tributary of the Mississippi River. It is the longest river in North America and drains the third largest area, though only the thirteenth largest by discharge. The Missouri's watershed encompasses most of the American Great...

 above the mouth of the Marias River

Marias River

The Marias River is a tributary of the Missouri River, approximately 210 mi long, in the U.S. state of Montana. It is formed in the Blackfeet Indian Reservation in Glacier County, in northwestern Montana, by the confluence of the Cut Bank Creek and the Two Medicine River...

. The highest point in the Highwood Mountains is Highwood Baldy at 2338 meters (7670 ft).

The area has volcanic origins and is rich in potash

Potash

Potash is the common name for various mined and manufactured salts that contain potassium in water-soluble form. In some rare cases, potash can be formed with traces of organic materials such as plant remains, and this was the major historical source for it before the industrial era...

. Many of the extrusive rocks and some of the dike

Dike (geology)

A dike or dyke in geology is a type of sheet intrusion referring to any geologic body that cuts discordantly across* planar wall rock structures, such as bedding or foliation...

 rocks contain abundant phenocrysts of a clear analcime that appears to be primary. Pseudoleucite

Leucite

Leucite is a rock-forming mineral composed of potassium and aluminium tectosilicate K[AlSi2O6]. Crystals have the form of cubic icositetrahedra but, as first observed by Sir David Brewster in 1821, they are not optically isotropic, and are therefore pseudo-cubic. Goniometric measurements made by...

 is an abundant constituent of many of the igneous rocks.http://www.minsocam.org/ammin/AM23/AM23_837.pdf The Shonkin Sag

Shonkin Sag

The Shonkin Sag is a prehistoric fluvioglacial landform located along the northern edge of the Highwood Mountains in the state of Montana in the United States. The Sag is a river channel formed by the Missouri River and glacial meltwater pouring from Glacial Lake Great Falls...

, a famous glacial meltwater channel, borders the Highwood Mountains to the north.