On the Lu-Kan-Shih : Studies on Mineralogical Chinese Drugs II

Lu-kan-shih was used in China at Sung dynasty, 10th century, to prepare brass by adding to copper. It was after more than 600 years at Ming dynasty, 16th century, that its use as an eye-wash was invented and it was listed in "Pen Ts' ao Kang Mu" edited by Li shih Chen. Lu-kan-shih is not found in Japan and is imported from China. Lu-Kan-shih which is now available in China is as large as a soy bean and its shape is pisolitic, amygdaloidal, reniform, botryoidal or irregular small cluster (Fig. 1). Its surface is covered with white powder, but its interior is entangled with white, pale brown and dark brown parts and shows banded concentric or reticulated structure similar to the cross section of agate or malachite (Fig. 2). By microscopic and X-rey examinations of Lu-kan-shih following minerals were found to be present : hydrozincite, dolomite and limonite (often calcareous). Hydrozincite forms a vein consisting of fine fibrous crystals and often gathers around the included minerals or small cavities in Lu-kan-shih. The order of crystallization is dolomite, hydrozincite and limonite. The former minerals are replaced or penetrated by the latter. By qualitative spectrochemical analysis of Lu-kan-shih following elements were detected: Zn, Na, Mg, Ca, Fe, Pb, Bi, Mn, Al, Ti, Cu. The molecular formula of hydrozincite calculated from the results of quantitative chemical analysis (Table 1 and 2)is 5ZnO・2 CO_2・3.5H_2O, and it coincides with that of Ford and Bradley proposed in 1916. These results show that hydrozincite is the main component of Lu-kan-shih and dolomite and limonite are minor constituents. The opinion adopted by several authors in China and Japan that smithsonite or smithsonite containing dolomite is the modern term for Lu-kan-shih was found to be erroneous. In Japan an eye-wash using the mixture of fruits of Rosaceae with Lu-kan-shih has been prepared in Kyoto since 1750 A. D. This recipe utilizes the dissolving action of citric or malic acid contained in the fruits on hydrozincite in Lu-kan-shih.