Glauconite from Latorpian Regional Stage was investigated. Glauconite grains have globular (rounded, oval) and biomorphic (only in limestone) shapes and show a wide range of green hues. The chemical and mineralogical composition of the glauconite grains were investigated using TEM and XRD methods. X-ray data by DRON- 2 (Co Ka radiation), TEM data were obtained by JEM 1200. The TEM data were calculated based on the method, developed by Srodon et all (SRODON et all, 1992). The studied glauconite grains are represented by mixed layered glauconite-smectite. TEM investigations recognize the increase of smectites from 25 to 40-45 % from sandstones to limestones. XRD investigations of the same samples reveal the less amount of smectite-from 10 to 20 %. Difference in TEM and XRD measurements may result from the usage of particles less then 5 um size in TEM investigation.The amount of smectite in light- and dark-green grains is similar, but the quantity of Fe decreases in light colored grains.