The value of nonfuel mineral production in Delaware in 2001 was about $13.1 million, according to estimated data compiled by the US Geological Survey. However, this figure reflects only the state's production of construction sand and gravel (2.42 million metric tons). Production data for Delaware's other significant nonfuel mineral, magnesium compounds produced for use in chemical and pharmaceutical manufacturing, was withheld to protect company proprietary data. Delaware ranked fourth nationally in production of magnesium compounds and was one of only five states that produced them in the US. They are extracted from seawater close to the mouth of the Delaware Bay near Lewes and, with aluminum hydroxides, are used in the manufacture of antacid products.