Rockhounding is the collection of reasonable amounts of mineral specimens, rocks, semi-precious gems, petrified wood and invertebrate fossils. Invertebrate fossils are the remains of animals that didn't have bones such as shellfish, corals, trilobites and crinoids.
A brief geology of granite. The geology of Cornwall and Devon consists primarily of granites, sandstones and slates. Over millennia, episodes of extreme compression, submersion, heat and erosion have exposed the granites that now provide many of the visually distinctive features in this part of the country.