Most of the nearly 5000 natural history collections of the Szekler Museum of Csík were transferred to our institution between 1971–1988. After the turn of the century in '89, the collection stopped growing, partly due to a lack of specialists and partly due to scarce financial resources. In the last few years, starting in 2018, a comparative archaeozoological collection has been added to the existing ones in the natural history department, precisely at the initiative of the right specialist.

• Mineral water: The material, which includes nearly 1500 objects, includes advertising labels of old mineral water bottling plants, as well as various types of bottles, jugs and bottle washing equipment for storing mineral water.

• Herbarium: The collection contains valuable dried herbs, the earliest dating from 1835. The herbarium of the Roman Catholic High School of Miercurea Ciuc, compiled between 1935 and 1937; the collection of plants "Flora Hungarica" by Lajos Richter (1880–1887) and last but not least the herbarium of the Institute of Pharmacy of Târgu Mureș (1880–1887).

• Birds and mammals: stuffed animals belonging to the typical fauna of the area, daytime predators: goshawk, kestrel, eagle owl; nocturnal predators: tawny owl, owls; field animals: emperor bird, black stork, brown hare, rabbit, partridge; woodland animals: grouse, pine grouse, green jay, brown bear, wolf, fox, lynx; waterfowl: waders, black guillemot, black-bellied teal, otter. The deer and roe deer ducks deposited in excellent condition by the County Fishing and Hunting Society are also very impressive.

• Minerals and rocks: The collection reflects mostly the most representative mineral and rock types from the Ciuc Basin and Transylvania, but also preserves various mineral types from Germany, the Czech Republic and China. Only a few mineral categories are mentioned as examples: mineral elements (mercury, sulphur); sulphides and sulphosalts (galenite, cinnabarite, pyrite, chalcopyrite); halides (rock salt, fluorite); oxides and hydroxides (quartz, amethyst, opal); carbonates (calcite, rhodocrosite, dolomite); sulphates (gypsum, barite); silicates (muscovite, sodalite, nepheline).

• The majority of the collection consists of rock types. The deep rocks include granite, which occurs only in small patches on the surface. It occurs on the eastern border of Tomești and is reddish in colour. Sienite, a transitional rock, is found in the Gheorgheni Basin, on the Piricske Hill on the inner side of the Eastern Carpathians.

• Andesite is the most important of the volcanic eruptive rocks. It is the largest and most beautiful andesitic volcanic range in Europe, stretching from Vatra-Dornei to Malnaș-Băi. Among the andesite varieties, the most important are the amphibole andesite of the Harghita range, which is found in the middle valley, the pyroxenic andesite, which is found in larger masses, and the basaltic andesite, a glassy-broken andesite variety. The most important transitional element towards basalts. In waterlogged areas, andesite is disrupted by carbon dioxide and hydrogen sulphide gases emitted in the volcanic aftermath, as well as by the carbonic waters themselves, giving rise to various post-volcanic alterations: kaolinic, quartzitic, alumitic and chloritic. The Harghita ridge on both sides is accompanied by debris of all sizes, ejected and deposited by former volcanic activity. The fine-grained rock, usually less than 2 mm in size, is called tufa, a solidified fragment of rock of various compositions.

• Metamorphic rocks include various types of shale, gneiss and marble. The most beautiful white marble is found under the church hill in the village of Lăzarea. The most important sedimentary rocks are conglomerate, breccia, clay, sandstone, gypsum, various types of limestone and peat. 

• A small part of the collection is made up of fossils: Pecten, Echinolampas, Ostrea, Belemnites, Amonites, Sigillaria, Lepidodendron, Numulites.

• Archaeozoological comparative collection: The comparative collection, essential for archaeozoological studies, consists of mammal and bird bones, mostly from archaeological finds, and less frequently from taxidermist-ordered fossil specimens.