Hughes Mountain Natural Area in southern Washington County, is a combination of igneous glades and three types of forest. The area was designated a natural area in 1982 to protect its unique geology and natural communities.

The igneous knob is named for John Hughes, the first European settler in the area, who arrived in 1810. The land stayed in the Hughes family until purchased by the Conservation Department.

The precambrian rock outcrops on Hughes Mountain are among the oldest (approximately 1.5 billion years) exposed rocks in the United States. The rocks were once liquefied by ancient volcanoes associated with the St. Francois Mountains. Some of the molten rock contracted and cracked as it cooled to create multi-sided columns. A rhyolite formation, known locally as the Devil's Honeycomb, is one of Missouri's geologic wonders, and is the highest point on Hughes Mountain.

Two-thirds of the area is wooded. The forest is dominated by post and white oaks with areas of stunted specimens of blackjack oak and black hickory.

The area's glades are natural openings on western or southern slopes and are dominated by native grasses and a variety of wildflowers. Glades occur where the soils are extremely thin and usually include areas of exposed bedrock. The thin soils, combined with the south and west exposure create a uniquely harsh habitat. Glade plants include little bluestem, broomsedge, poverty grass, the small but colorful flame flower, prickly pear cactus, yellow star grass, spiderwort, and wild hyacinth. Animals often found on these glades includes several species of lizards, lichen grasshoppers, and prairie warblers. Exposed rocks within glades are often covered with a variety of lichens.