Mashuk (Russian: Машук) is an isolated mountain in the North Caucasus overlooking the city of Pyatigorsk in Stavropol Krai in Russia. The height of the mountain is 993 m. Mashuk is a laccolith with a crystal nucleus, buried under sedimentary rock (limestone and marl of Upper Cretaceous and Palaeogene). The top of the mountain is flattened and domelike. There is a cavern called "Proval" (depth - 20 m) on the southern slope of Mashuk.