Two moderately shocked rock samples collected from the Ries Crater, West Ger-many (granite--gneiss sample RC--647--29 and biotite-granite sample RP--627--55) and twoweakly shocked pegmatite samples (Lj--711--12 and Lj--711--5) taken from Lake Lappaja-rvi, Finland, have been optically studied to establish the variation range of optical constantsand distribution characteristics of shock lamellae in shocked quartz. It has been found that sample RC--647--29 contains shocked quartz grains with the ave-rage refractive index ranging from 1.4612 to 1.5331, and sample RP--627--55 from 1.5002 to1.4669, i.e., they cover a wide range of shock pressures. As for the larger quartz grains in sam-ples Lj--711--12 and Li--711--5, the variation range of the average refractive indices are smal-ler than those of samples from the Ries Crater. Hence the estimation of degree of shock mustest with the investigation of a set of representative shocked quartz crystals from a single shoc-ked rock sample. The optical data on shocked quartz indicate that the degree of shock is highly independentof the number of shock lamellae sets and their orientations; the most sensitive optical indicatoris the index of refraction. On the basis of TEM investigations of single crystal grains of shocked quartz differing inrefractive index, three mechanisms of formation of shock lamellae have been established: hostquartz crystals with lamellae having closely spaced dislocations; host quartz crystals with lamel-lae of randomly oriented fine grains of quartz; and host quartz crystals or their residual frag-ments with lamellae of silica glass. Two moderately shocked rock samples were collected from the Ries Crater, West Ger-many (granite-gneiss sample RC-647--29 and biotite-granite sample RP- 627-55) and twoweakly shocked pegmatite samples (Lj-- 711--12 and Lj - 711--5) taken from Lake Lappaja-rvi, Finland, have been optically studied to establish the variation range of optical constants and distribution characteristics of shock lamellae in shocked quartz. It has been found that sample RC - 647--29 contains shocked quartz grains with the ave-rage refractive index ranging from 1.4612 to 1.5331, and sample RP - 627--55 from 1.5002 to 1.4669, ie, they cover a wide range of shock pressures. As for the larger quartz grains in sam-ples Lj - 711--12 and Li - 711--5, the variation range of the average refractive indices are smal-ler than those of samples from the Ries Crater. Therefore the estimation of degree of shock mustest with the investigation of a set of representative shocked quartz crystals from a single shoc-ked rock sample. The optic al data on shocked quartz indicate that the degree of shock is highly independent of the number of shock lamellae sets and their orientations; the most sensitive optical indicatoris the index of refraction. On the basis of TEM investigations of single crystal grains of shocked quartz differing in refractive index , three mechanisms of formation of shock lamellae have been established: hostquartz crystals with lamellae having closely spaced dislocations; host quartz crystals with lamel-lae of randomly oriented fine grains of quartz; and host quartz crystals or their residual fragmets with lamellae of silica glass.