The geological collections comprise about 15,000 minerals and 8,000 rocks. Special features include, for example, the Diekmann mineral collection with over 10,000 samples from the Sauerland ore mining industry. The rock collection includes the Serafim collection with thousands of ice age debris from Westphalia and samples from the places of origin in Scandinavia.
Objects in the reference collections come from all over the world - they allow comparisons and classification of the Westphalian finds. In addition, the museum owns some meteorites, including a lunar meteorite.