The compound Na2SO4 is called sodium sulfate. It occurs naturally in many places in the world, including Canada, Mexico, China, South Africa and Spain. It exists in Washington, Wyoming, Nevada and Utah in the United States.
Sodium sulfate is an important compound in the chemical industry and is used widely in the manufacturing of soap and detergent. Sodium sulfate develops naturally when igneous rocks erode and release sodium into nearby water. When that sodium reacts with sulfur from one of a number of possible sources in the environment, sodium sulfate is the resulting precipitate. The mineral thenardite, a naturally occurring sodium sulfate, occurs in salt lakes, such as the Great Salt Lake in Utah.