The Red Cap claims are underlain by Upper Triassic Stuhini Group rocks comprised mainly of andesitic to basaltic flows, volcanic breccia, agglomerate tuffs, and minor volcanic sandstones. These are disconformably underlain by the King Salmon Formation, which is part of the Triassic Stuhini Group and is comprised of thick-bedded, dark greywacke, conglomerate, mudstone, siltstone, and shale with minor volcanic flows, tuffs, breccia, limy shales, and limestone.

The Stuhini Group rocks are intruded by a Cretaceous hornblende- biotite granodiorite stock which may be part of the Coast Plutonic Complex, and by feldspar porphyry dykes, which are thought to be re- lated to the Tertiary-Cretaceous Sloko Group volcanics.(GSC Map 1262A)

Graphite is reported to occur on the top of a ridge about 1.6 kilometres northwest of Mount Lester Jones. Samples weighing more than 0.5 kilogram were collected and were described as high-grade graphite with a somewhat sheared texture. The graphite is thought to be fissure vein-type material. No coal or carbon, from which graphite might be formed, has been reported in the Stuhini Group rocks. In this vicinity the Stuhini volcanic rocks are intruded by a small Jurassic or Cretaceous augite diorite stock.