COMMON ROCKS

(Igneous, Sedimentary, Metamorphic)

 

IGNEOUS ROCKS

Igneous rocks form by the cooling & crystallization of hot, molten rock (magma & lava).  If this happens at or near the land surface, or on the seafloor, they are extrusive igneous rocks.  If this happens deep underground, they are intrusive igneous rocks.

Most igneous rocks have a crystalline texture, but some are clastic, vesicular, frothy, or glassy.

 

 

GRANITE      BASALT & OLIVINE BASALT     ANDESITE

 

RHYOLITE                     GABBRO                         DIORITE

 

PORPHYRITIC GRANITE                        PUMICE

 

PORPHYRITIC RHYOLITE                     SCORIA

 

PORPHYRITIC BASALT             VESICULAR BASALT

 

OBSIDIAN                       SNOWFLAKE OBSIDIAN

 

VOLCANIC BRECCIA       VOLCANIC TUFF

 

ANORTHOSITE                     PERIDOTITE

 

QUARTZ  MONZONITE

 


 

Classification of igneous rocks (according to the British Geological Survey) (662 kb pdf)

 


 

SEDIMENTARY ROCKS

Sedimentary rocks form by the solidification of loose sediments.  Loose sediments become hard rocks by the processes of deposition, burial, compaction, dewatering, and cementation.

If the sediments are derived from weathering & erosion of any previously existing rocks, you’ve got siliciclastic sedimentary rocks.

If the sediments are derived from once-living organisms (plants, animals, micro-organisms), you’ve got biogenic sedimentary rocks.

If the sediments formed by inorganic chemical means, you’ve got a chemical sedimentary rock.

Most sedimentary rocks have clastic textures, but some are crystalline.

 

CONGLOMERATE             BRECCIA             ARKOSE

 

SANDSTONE & GRAYWACKE      SILTSTONE      SHALE

 

LIMESTONE                COQUINA                CHALK

 

OOLITIC LIMESTONE          ONCOLITIC LIMESTONE

 

CHERT          BANDED IRON FORMATION          PEAT

 

LIGNITE COAL     CANNEL COAL     BITUMINOUS COAL        

 

DOLOSTONE          ROCK SALT          ROCK GYPSUM

 

DIATOMITE            OIL SHALE            TAR SANDSTONE

 

BAUXITE                PHOSPHORITE

 


 

Classification of sedimentary rocks (according to the British Geological Survey) (459 kb pdf)

 


 

METAMORPHIC ROCKS

Metamorphic rocks result from intense alteration of any previously existing rocks by heat and/or pressure and/or chemical change.  This can happen as a result of regional metamorphism (large-scale tectonic events, such as continental collision or subduction), burial metamorphism (super-deep burial), contact metamorphism (by the heat & chemicals from nearby magma or lava), hydrothermal metamorphism (by superheated groundwater), shear metamorphism (in or near a fault zone), or shock metamorphism (by an impact event).

Many metamorphic rocks have a foliated texture, but some are crystalline or glassy.

 

MARBLE       QUARTZITE       GREENSTONE       EPIDOTITE

 

DOLOMITIC MARBLE       SOAPSTONE       ECLOGITE

 

SLATE       PHYLLITE       SCHIST       GNEISS       MIGMATITE

 

GRANULITE       CHARNOCKITE       TECTONITE       SKARN

 

ANTHRACITE  COAL       METACHERT       SERPENTINITE

 

METACONGLOMERATE       TECTONIC  BRECCIA

 

HORNFELS       GARNETITE

 


 

Classification of metamorphic rocks (according to the British Geological Survey) (260 kb pdf)

 


 

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