ABSTRACT

The heavy minerals of the Huronian quartzite of the Baraboo Range consist mostly of zircon and rutile. There are occasional grains of biotite and apatite and rare grains of amphibole, augite, and magnetite. Secondary minerals are hematite and chlorite. No tourmaline was found in the quartzite, and only a single grain of garnet was seen. The heavy minerals in the quartzites are not different from those in the underlying igneous rocks.

Zircon and tourmaline are common heavy minerals in the Paleozoic rocks. These rocks contain an abundance of garnet outside the Range, but this mineral is rare within the Range.

The extreme rareness of garnet and the apparent absence of tourmaline in the Huronian quartzite show that the materials for the Paleozoic sandstones were largely derived from sources other than the rocks of the Range and the rareness of garnet in the sandstones within the Range indicates that only limited quantities of sands were introduced from the outside.