The geology collection contains over 30,000 rocks, minerals and fossils which were found mainly across Hampshire and the Isle of Wight. The fossil collection comprises animal, fish and plant specimens dating back over 200 million years, found in both marine and terrestrial deposits. The rock and mineral collection contains numerous crystalized rock specimens of stratigraphic and regional significance.

The collection contains material from William Curtis, Herbert Druitt, George Willis and Reginald Hooley, which include Quaternary mammals, Palaeogene molluscs, particularly from Barton on Sea, and Late Cretaceous echinoderms from various Hampshire Chalk localities. Other collections made by these individuals include an important collection of silicified molluscs from the Cretaceous of Devon and Early Jurassic Cephalopods from Dorset and Yorkshire.

The geology collection is used as an aid to inform people about important issues relating to the biodiversity and geological history of Hampshire and the complex biological and geological processes involved. The geology collection is used extensively by individual researchers, universities and organisations for scientific research and training.

More recent collections and individual specimens obtained by the Hampshire Cultural Trust continue to provide new, previously unrecorded information on the geology of Hampshire, including new localities, abundance, diversity, distribution and preservation of the fossil faunas.