KUNKAR. HIND. Nodular, tufaceous, traver tine-like deposits of carbonate of lime. It is formed in all soils by the action of springs, like the travertines of Italy. In some places it is a pure carbonate of lime ; in others it is a concreted limestone or pisolite ; these, kinds are used for road-making.
It is a Hindustani word, meaning nodule. There are two varieties, the red and the white ; the red differs from the white solely in containing a large proportion of peroxide of iron ; the white consists of carbonate of lime, silica, alumina, and sometimes magnesia and protoxide of iron. Kun kar is also deposited by calcareous waters abound ing in infusorial animalculre ; the waters of the annual inundations are rich in lime, and all the facts that have come under observation appear to indicate that this is the source of the kunkar deposit, which is seen in a different form in the Italian travertine, and the crescentic nodules of the Isle of Sheppey and of Boulogne. Kunkar is mostly nodular,—always fresh water and recent,— in most cases in the act of 'being formed under our eyes. It is sometimes found in thick stratified beds like the travertine near Rome, and seems in this case to have been formed by calcareous springs. More generally it is met with in clay or alluvial soil, in the shape of small pieces from the size of peas or filberts to that of the hand. In the blue clay which stretches along the Indian shores, it is found in vast abundance, generally assuming the most fantastic forms ; indeed, it abounds in every rice field and open soil all over the country. The more recent varieties seem to be formed by the agency of the rains. When the earth abounds
with vegetation, the tepid waters are charged with fixed air, and dissolve the lime prevailing in the soil everywhere around, the mineral being again thrown down as the advancing season dispels the excess of gas. It in this state absorbs the clayey matter around, and cements it into kunkar. This is collected by the lime-burner, placed with fire wood in small-sized conical kilns, and burnt in the usual way. It contains 72 of carbonate of lime, 15 of sand, and 11 of clay and oxide of iron ; but usually about 70 per cent. of carbonate of lime, about 2} per cent. of carbonate of magnesia, a trace of oxide of iron, and 10 to 20 per cent. of sand and clay. Mixed with half its weight of river sand, it makes an excellent mortar ; burnt in pieces of a cubic inch or so in size, and then powdered without slaking, it forms a first-rate water cement, setting in a few minutes, and be coming as hard as 'stone. The finer varieties of kunkar are burnt with charcoal all throughout the country, in neat pigmy-looking kilns, 21- feet high and about as much in diameter at the base. These hold about a cubic foot of material, or about 36 lbs. of charcoal and kunkar in equal parts. When burnt and slaked, it is then made up into bricks, which are sold in the bazar for the purpose of whitewashing. The ordinary Indian cement is chunam in its various forms. The only Indian building materials which differ materially from those of the rest of the world are laterite, concrete, and kunkar. — Col. Sykes, Lond. Geol. Trans., 1836; Dr. Buisc; O'Shaughnessy.