The runoff is rich in the element boron and is highly concentrated by evaporation in the arid climate. Eventually the concentration is so great that crystals of borax and other boron minerals form. Ground water flowing through the borax sediments at the bottom of the playa is believed to react with the borax and form other minerals such as colemanite. Colemanite forms small but richly faceted crystals. The short prismatic habit is typical and good crystals with complicated faces are sought after by collectors.
Color is white to clear.
Luster is vitreous. Transparency crystals are transparent to translucent. Equant crystals that appear stubby and bead-like are also common. The crystals are sometimes flattened and can appear bladed. The terminations are either blunted or steeply pyramidal.