Industrial mineral site no. 1783, known as "Double Hill Deposit #4" is a site in San Juan County, Washington. This site has been associated with limestone and marble. A notation found in DGER Bulletin 52 on page 155-156 says "Very little is known about the geology of this limestone due to lack of exposure and to thick vegetation and soil cover", and designates the value as "The sugary texture seen in the outcrops suggests that most of the limestone contains a considerable amount of dolomite. Silica in the form of jasperoid is a common impurity".