The Chiwaukum Mountains are a north-south mountain range

Mountain range

A mountain range is a single, large mass consisting of a succession of mountains or narrowly spaced mountain ridges, with or without peaks, closely related in position, direction, formation, and age; a component part of a mountain system or of a mountain chain...

 in central Washington, USA. They stretch from Snowgrass Mountain at 47°41′N 120°56′W, to 47°45′N 120°54′W.

The mountains are made of schist

Schist

The schists constitute a group of medium-grade metamorphic rocks, chiefly notable for the preponderance of lamellar minerals such as micas, chlorite, talc, hornblende, graphite, and others. Quartz often occurs in drawn-out grains to such an extent that a particular form called quartz schist is...

, part of the Nason terrane

Terrane

A terrane in geology is short-hand term for a tectonostratigraphic terrane, which is a fragment of crustal material formed on, or broken off from, one tectonic plate and accreted or "sutured" to crust lying on another plate...

. The original rock in the Nason terrane was laid down 210 Myr ago. The terrane then smashed into the western coastline of the continent, and the Mount Stuart

Mount Stuart

Mount Stuart is a mountain in the Cascade Range, in the U.S. state of Washington. It is the second highest non-volcanic peak in the state, after Bonanza Peak and tenth-highest overall...

 batholith

Batholith

A batholith is a large emplacement of igneous intrusive rock that forms from cooled magma deep in the Earth's crust...

 intruded into it in the late Cretaceous

Cretaceous

The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...

. The intrusion of the granitic rock metamorphosed the rock into schist. http://geopubs.wr.usgs.gov/i-map/i1661/chelpama.pdf.

Partial list of peaks:

• Big Chiwaukum - 8,081' (2463m)
• Snowgrass Mountain - 7,993' (2436m)
• Big Jim Mountain - 7,765' (2367m)

Nearby peaks:

• Jim Hill Mountain - 6,765' (2062m)
• Cowboy Mountain - 5,853' (1784m)