Scawtite，a rare carbonated calcium silicate hydrate mineral，was discovered at the Fushan mine, Hebei Province in 1982. It occurs in cavities of the magnesian skarn near the contact zone, coexisting with calcite, scolecite, tobermorite,gyrolite and thaumasite. Its colorless and transparent crystals look like rectan gular tablets with such forms as谧100}，{010}，谧101}.{120}，{201}，{301}，{211}，{311} and{611}.Its optical constants are Ng=1.629，Nm=1.615, Np=1.609，(+)2V=67º.c∧Ng=30~35º,and its specific gravity is 2.76. The structural parameters, determined on a Nicolet-R 3 four-circle diffracto- meter, are as follows: space group I2/m. ao=10.1206 A,bo=15.2058A,co=6.6345A， β=100º37′and Z=2. The data obtained from microprobe analysis and loss in weight on ignition give a structural formula of (Ca7.03Fe0.01Mn0.01K0.002) (Si6018)0.98(CO3)1.06·2.1H20. X-ray diffraction shows the spacings and intensities of the five stronger lines to be 3.02A(100)，2.99A(80)，2. 78A(35)，2. 49A(40)，and 1.896A(40) respectively. There are 21 abs6rption bands in the infrared spectra corresponding with the structure of scawtite. The stretch vibration of the CO3 group splits into two bands with wavenumber being 1486 and 1448cm-1 respectively.The explanation is that the CO3 triangles are horizontal isosceles ones with the length of one C-0 bond different from that of the other two C-0 bonds, thus reducing the symmetry from Dge to C2h and resulting in the disappearance of the degeneration and the split of the absorption band. The DTA curve shows two endothermic troughs at 240℃ and 7570 ℃ and an exothermic crest at 895℃, resulting respectively from loss of crystallizationwater, escape of CO2 and formation of wollastonite as a new phase. Scawtite is a typical low-temperature hydrothermal mineral formed at about 1000℃.