The first measurable triplite crystals to be recorded were found in the Mica Lode pegmatite, Eight Mile Park, Fremont County, Colorado. Two other new triplite localities are the School Section pegmatite in the same district and another pegmatite in El Paso County, Colorado. The triplite occurs in hydrothermal replacement units along the foot-wall sides of core pods. On the basis of crystallographic measurements of four crystals and x-ray examination of an oriented section, triplite is monoclinic, prismatic -2/m(?), with a0= 11.90, b0=6.48, c0=9.92, β = 105°53′. The space group is I 2/m? The optical properties and specific gravity of the Mica Lode material correspond closely with those of triplite from the 7U7 Ranch, Arizona, and it is believed that the chemical composition is also similar.