Abstarct: The agate-gasper mineralization area of Chah Andoo is located at 100 km of SW Damqan in Semnan Province. Basalt, andesite-basalt, tuff and mextamorphic rocks are the main rocks which expose in the study area. Agate, jasper and agate – jasper are silica minerals which widespread at the plain surface as crushed fragments from a few millimeters to 0.5 meter in dimension .Banded (mono centric), stalactite (landscape), mossy and thunder egg agates are the most frequent agate types in the area. Jaspers observe as banded, mossy, massive and different color types. Low quartz and moganite as the main silica polymorph minerals with impurities such as hematite, carbonate, chlorite and carbonaceous organic material was revealed by micro Raman spectroscopy. baxsed on the results of XPMA and XRF analyses oxides of Fe, Ca ,Mn and Cr are the main impurities in the agate and jaspers. Gemological investigation (color, texture, luster, transparency and specific gravity) show that agates and jaspers have good quality as gemstone. Moganite introduced in the silica mineralization for the first time in Iran.