BATUAN SEDIMEN

• Sedimentary Rocks • HardnessGrain SizeCompositionOtherRock

Typehardmixedmixed rocks and sedimentround rocks in sediment matrixConglomeratehard or softmixedmixed rocks and sedimentsharp pieces of same material as groundmassBrecciahardcoarseclean quartzwhite to brownSandstonehardcoarseclean quartz and feldsparusually very coarseArkosehardmixedmixed sediment with rock grains and claygray or dark and "dirty"Graywackehardfinevery fine sand; no clayfeels gritty on teethSiltstonehardfinechalcedonyno fizzing with acidChertsoftfineclay mineralsfoliatedShalesoftfinecarbonblack; burns with tarry smokeCoalsoftfinecalcitefizzes with acidLimestonesoftany sizedolomite (magnesian calcite)no fizzing with acid unless powderedDolomite or Dolostonesoftcoarsefossil shellsmostly piecesCoquinavery softcoarsehalitesalt tasteRock Saltvery softcoarsegypsumwhite or pinkGypsum

Sedimentary Rocks

Hardness Grain Size Composition Other Rock Type

hard mixed mixed rocks and sediment round rocks in sediment matrix Conglomerate

hard or

mixed mixed rocks and sedimentsharp pieces of same material as groundmass Brecciasoft

hard coarse clean quartz white to brown Sandstone

hard coarse clean quartz and feldspar usually very coarse Arkose

hard mixedmixed sediment with rock grains and clay gray or dark and "dirty" Graywacke

hard fine very fine sand; no clay feels gritty on teeth Siltstone

hard fine chalcedony no fizzing with acid Chert

soft fine clay minerals foliated Shale

soft fine carbon black; burns with tarry smoke Coal

soft fine calcite fizzes with acid Limestone

soft any size dolomite (magnesian calcite)no fizzing with acid unless powdered

Dolomite or Dolostone

soft coarse fossil shells mostly pieces Coquina

very soft coarse halite salt taste Rock Salt

very soft coarse gypsum white or pink Gypsum

A Basic Classification Derived From theSimple Ideal Model

• Classification of Environments by Depositional ProcessesTerrestrialTransitionalMarineAlluvial FanBraided RiverMeandering River(including alluvial plain)LakeDelta ComplexBeachLagoonTidal FlatDunesShelf (storm and tidal dominated)Submarine fanBasin CarbonateTidal FlatLagoonCarbonate Barrier (reef)ShelfBasin

• Petroleum geologists study very thin slices of reservoir rocks under a microscope to analyze the character of rock porosity and permeability. This thin section shows a conventional sandstone reservoir that has been injected with blue epoxy. The blue areas are pore space and would contain natural gas in a producing gas field. The pore space can be seen to be interconnected so gas is able to flow easily from the rock.