places and has long since ceased to be worked. Slate – This dense, fine grained metamorphic rock, which is produced from a fine clay, can be split into thin, smooth plates and is quarried throughout the district. It is suitable for roofing purposes, the thin dark blue slates being somewhat inferior in quality. Limestone – By burning this mineral, lime is procured which can be used as mortar. There are two distinct ranges of limestone hills in the district, the first, north of the Alaknanda in Nagpur, the second, running from Lohba patti to the Pinddar and again to the Alaknanda in patti Bacchansyun in district Garhwal. Reserves of dolomite exists in the district and tufaceous deposits are also found near several Nullahs. Building stone – Stone which can be used for building purposes is available in most parts of the district. Sandstone is found in abundance in the lower hills. Gneiss and chlorite schists which are available throughout the district are frequently used for building purposes. Sulphur – This yellow mineral, also known as brimstone is found in the district as green sulphate of iron and is obtainable from iron pyrites and copper mines, its presence being characterised by a small as of rotten eggs. Sulphur springs also occur in many parts in the district. Bitumen – The brownish white natural sulphate of alumina known as Shilajit is found in rocks at a fairly high altitude and occur in small lumps which generally have an admixture of red sand and micaceous stone embedded in them. It is used in Ayurvedic medicine and during the season when there is an influx of pilgrims, it fetches good income to those who deal in it. Some other minerals found in the district are antimony, arsenic, lignite or brown marble, mica and silver. Physiographically the district, which lies in a region of tectonic or folded and overthrust mountain chains, has strata are structurally marked by complex folds, reverse faults, overthrusts and nappes of great dimensions, all these as well as frequent earthquake of varying intensity give region to believe that the region is still unstable. Although any movement or tremor of the Earth's crust in the district is not produced by volcanic activity, the Chaukhamba peak a pair to be the crater of an extinct volcano. Climate As the elevation of the district ranges from 800 m to 8,000 m above sea level