The quartzite is an island among flood basalts. It is also an island from the Missoula floods. The floods were about 2700 feet above sea level in this area whereas the butte is 3615 feet above sea level. 

Steptoe Butte

Steptoe Butte is a quartzite island jutting out of the silty loess of the Palouse hills in Whitman County, Washington, in the northwest United States. The 3,612-foot (1,101 m) butte is preserved as Steptoe Butte State Park, a publicly owned 150-acre (61 ha) recreation area located 12 miles (19 km) north of Colfax. Steptoe Butte and Kamiak Butte comprise Steptoe and Kamiak Buttes National Natural Landmark.^[3]

• http://en.wikipedia.org/wiki/Steptoe Butte
• https://www.google.com/maps/d/u/0/viewer?mid=14YY3J0HLMehpL22SVtE7LYReVC80PyxR&hl=en&ll=47.04358646873962%2C-117.30372940099625&z=14