The lodes occur in Silurian metamorphic micaceous schists, intruded by granite, porphyry and diorite, and traversed by numerous quartz reefs, some of which are gold-bearing.
It is used as a pigment (cadmium yellow), for it retains its colour in an atmosphere containing sulphuretted hydrogen; it melts at a white heat, and on cooling solidifies to a lemon-yellow micaceous mass.
The latest Cretaceous is the Ripley formation, which lies west of the northern part of the last-named, and, about Scooba, in a small strip, the most southerly of the Cretaceous - it is composed of coarse sandstones, hard crystalline white limestones, clays, sands, phosphatic greensands, and darkcoloured, micaceous, glauconitic marls; its greatest thickness is about 280 ft.
Another well-known bed, formerly known as the "Bristol" or "Lias" Bone Bed, exists in the form of several thin layers of micaceous sandstone, with the remains of fish and saurians, which occur in the Rhaetic Black Paper Shales that lie above the Keuper marls in the south-west of England.
High - is decorated with designs in black, white, green and yellow, the yellow designs (formed of micaceous sand) glistening like gold.