The Rock Collection now consists of over 100,000 specimens and has worldwide coverage. A prototype search-engine of 20,000 entries is now accessible.
Because the main part of the collection is housed in acquisition order, it has always been necessary to maintain full indices of locality and rock type. To facilitate rapid use of the collection by visitors and research workers, a number of catalogues have been published. The fullest are those on Africa and America (Campbell Smith, 1928 and 1932) and Antarctica and Australasia (Campbell Smith and Game, 1954). A single-volume catalogue has been published by Bishop et al. (1971, reprinted 1984) and a catalogue of the chemically analysed igneous rocks by Moore et al. (1979). These will be made available in electronic form at a future date.
The collection is notably strong in igneous rocks, specimens from oceanic islands and collections made by major expeditions, particularly from the Antarctic, Africa and Australia. In the nineteenth century an important source of material was expeditions of exploration such as those of Captain Flinders in 'Investigator' in 1801-03, the 'HMS Challenger' expedition of 1872-76 and the early Geological Society expeditions of the former British colonies by well-known geologists such as Lyell, Murchison, Greenough and Selwyn. Purchase also played an important part in the growth of the collection during this period, notably that of Italian rocks from Teodoro Monticelli in 1823. Many of the early collections, such as those made by Captain Scott and Ernest Shackleton, and the small suite of rocks collected during the fateful ascent of Mount Everest by Mallory and Irvine, are not only significant for their historical value. These 'voyages of discovery' have helped us to map the geology of the earth and discover new economic resources. Some have even brought to light or redirected geological theories about the dynamic processes that have shaped the landscape. The theory of Nappe Tectonics was developed from examination of the exposure of the root of the Alps during the excavation of the 19km long Simplon Tunnel in 1905. Increasingly, material has been obtained, guided by the Museum's acquisitions policy, specifically for its intrinsic scientific interest. An example is the fine collection of xenoliths from kimberlites donated by Prof Peter Nixon in 1994. In recent years a high proportion of the rock specimens have been collected by members of the Museum staff for research purposes.
The exceptionally wide coverage, notably of igneous rocks, and more particularly (alkaline rocks and carbonatites), and the many localities which are commonly difficult to access, especially oceanic islands, generates a demand for research and comparative material from researchers, particularly igneous petrologists. Every means is taken to facilitate such work either by making the hand specimen and thin sections available for study, or providing small 'off-cuts' of rock for sectioning or chemical analysis.
In February 2002, a new exhibit was completed, illustrating the origins, classification and significance of the three main rock groups: igneous, metamorphic and sedimentary. Situated in the window displays of Gallery 102 (Mineral Gallery ), this exhibit has provided an opportunity to display specimens from the collection that the public rarely see. Notable examples are a conglomerate from the Falkland Islands collected during the 'Challenger' expedition, a polished slab of metamorphosed rock collected by Sir William Hamilton from the Vesuvius area, and some fresh, rare extrusive carbonatite lava from an eruption in October 2000.
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