The Frasch process is a method to extract sulfur from underground deposits. It is the only economic method of recovering sulfur from elemental deposits. Most of the world's sulfur was obtained this way until the late 20th century, when sulfur recovered from petroleum and gas sources (recovered sulfur) became more commonplace (see Claus process).
In the Frasch process, superheated water is pumped into the sulfur deposit; the sulfur melts and is extracted. The Frasch process is able to produce high purity sulfur.
As of 2011, the only operating Frasch mines worldwide are in Poland and since 2010 in Mexico. The last mine operating in the United States closed in 2000. A Frasch mine in Iraq closed in 2003 due to the U.S. invasion of Iraq.
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“Rules and particular inferences alike are justified by being brought into agreement with each other. A rule is amended if it yields an inference we are unwilling to accept; an inference is rejected if it violates a rule we are unwilling to amend. The process of justification is the delicate one of making mutual adjustments between rules and accepted inferences; and in the agreement achieved lies the only justification needed for either.”
—Nelson Goodman (b. 1906)