The heavy minerals deposited by the South Canadian River are magnetite, ilmenite, garnet, epidote, rose, pink, green, and black tourmaline, hematite, and purple, transparent, and brown zircon. These minerals are present in the river deposits throughout New Mexico and Texas, but decrease in abundance downstream as far as the Amarillo region. Below Amarillo magnetite, epidote, ilmenite, garnet, rose tourmaline, and hematite increase. Boulders are composed of granite, basalt, and sandstone. They are large, abundant, and angular near the source of the stream, but are absent in the eastern part of the Texas Panhandle. Tributaries flowing across basaltic lava flows carry an abundance of tourmaline; however, this mineral is of minor importance when the sediments are derived from granites. Other tributaries that secure their sediments from Triassic and Tertiary sedimentary rocks deposit the same heavy minerals as the river.