is 6.5 to 7.5. Without cleavage. Mineral which often occurs in metamorphic rocks, sometimes in igneous rocks.geologic cross-sectiongeologicky rezA representation of a portion of the earth in a vertical plane.geologic time scalegeologicka casova skalaGeologic term, which means mirroring of Earth history expressed in a form of geologic periods.geologygeologieScientific branch studying origin and development of the Earth and other planets.geophysicsgeofyzikaThe application of physical laws and principles to a study of the earth.geothermal energygeotermalni energieThermal energy produced by the Earth. Some sources of this energy can be harnessed and used by a man.geothermal gradientgeotermalni gradientRate of temperature increase associated with increasing depth beneath the surface of the earth (normally about 25!C/km).geysergejzirA type of hot spring that periodically erupts hot water and steam.geyseritegejziritA deposit of silica that forms around many geysers and hot springs.glacial agedoba ledovaGeologic period in Quaternary, when glaciers were advancing.glacial budgetSum of advancing and receding of glacier per one year (positive and negative).glaciationzaledneniGeneral term for covering of the Earth surface by a glacier.glacierledovecA large, long-lasting mass of ice, formed on land by the compaction and recrystallization of snow, which moves because of its own weight.glacier recessionustup ledovceReceding of a glacier.glacier tonquesplaz ledovce"Freezing stream shaped" accumulation of ice on edge of a glacier.glassy lusterskelny leskA luster that gives a substance a glazed, porcelainlike appearance. See vitreous luster.glauconiteglaukonitDark green coloured clay mineral occuring in some sands and sandstones. Properties see clay minerals.gneissrulaA metamorphic rock composed prevailingly of quartz, feldspars and micas arranged in plane parallel structure.grabenprikopova propadlinaA down-dropped block bounded by normal faults.graded bedA single bed with coarse grains at the bottom of the bed and progressively finer grains toward the top of the bed.graded beddinggradacni zvrstveniAn arrangement of layers of clastic sediments and sedimentary rocks. Each layer has different size of particles and granularity of layers tends topward from coarse to fine.granitegranitA felsic, coarse-grained, intrusive igneous rock composed mostly of quartz, feldspars and often containing micas. It belongs to group of granitoids.granite porphyrzulovy porfyrDike rock with composition similar to granite. It differs only by a texture and structure.granitoidsgranitoidyA group of "granite like rocks", which differs from each other only by type of feldspar.granoblastic texturegranoblasticka strukturaTexture of metamorphic rocks, which is characterized by "grain shaped" minerals, e.g. marble.granodioritegranodioritIgneous plutonic rock belonging to group of granitoids. It has composition similar to granite except the ratio between types of feldspar (plagioclases>K-feldspars).granulitegranulitHigh-grade metamorphic rock, ligh-grey coloured. It is composed of quartz and feldspars, mostly with presence of small garnet grains.graphic texturepismenkova strukturaSpecial texture created by intergrowth of feldspars and quartz, which looks like hieroglyfic letters.graphitegrafitMineral formed of carbon. Gray to black in colour. Hardness is 1. It may have dull luster, greasy feel, soils paper and fingers.gravelsterkSediment composed of rounded particles coarser than 2 mm in diameter.greywackedrobaA sandstone with more than 20% of unstable particles and feldspars within psammitic fraction and more then 15% of finegrained matrix.ground morainespodni (bazalni) morenaA blanket of till deposited under a glacier or released as glacier ice melted.groundmasszakladni hmotaThe material between the phenocrysts in porphyritic igneous rock. It includes the basis or base as well as the smaller crystals of the rock.