Content Composition of Earth Crust Minerals Groups Silicates Structures Silicates Minerals Nonsilicate Minerals

Composition of Earths CrustNearly 4000 minerals have been namedRock-forming mineralsCommon minerals that make up most of the rocks of Earths crustOnly a few dozen membersComposed mainly of the 8 elements that make up over 98% of the continental crust

Elemental abundances in continental crust

Minerals Groups Silicate Olivine Pyroxene Micas Clay Feldspar Quartz Nonsilicate Minerals

Questions

Silicate MineralsSilicatesMost important mineral groupComprise most rock-forming mineralsVery abundant due to large % of silicon and oxygen in Earths crustSilicon-oxygen tetrahedronFundamental building blockFour oxygen ions surrounding a much smaller silicon ion

Two illustrationsof theSiO4tetrahedron

Joining silicate structuresSingle tetrahedra are linked together to form various structures includingIsolated tetrahedraRing structuresSingle and double chain structuresSheet or layered structuresComplex 3-dimensional structures

Questions

Mineral groupsCommon silicate mineralsDark silicates: Olivine groupHigh temperature Fe-Mg silicatesIndividual tetrahedra linked together by iron and magnesium ionsForms small, rounded crystals with no cleavage

Silicate MineralsDark silicates: Pyroxene groupSingle chain structures involving iron and magnesiumTwo distinctive cleavages at nearly 90 degreesAugite is the most common mineral in the pyroxene group

Silicate MineralsDark silicates: Amphibole groupDouble chain structures involving a variety of ionsTwo perfect cleavages exhibiting angles of 124 and 56 degreesHornblende is the most common mineral in the amphibole group

Hornblende amphiboleFerromagnesian minerals like hornblende and pyroxene tend to weather more easily than other minerals in plutonic rocks, like granite.

Cleavage angles for augite and hornblende

Questions

Silicate MineralsLight silicates: MicasExcellent cleavage in one directionProduces the glimmering brilliance often seen in beach sandMuscovite is Common member of the mica family

Silicate MineralsLight silicates: Clay mineralsClay is a general term used to describe a variety of complex mineralsClay minerals all have a sheet or layered structureMost originate as products of chemical weathering

Questions

Silicate MineralsCommon silicate mineralsLight silicates: QuartzOnly common silicate composed entirely of oxygen and siliconHard and resistant to weatheringConchoidal fractureOften forms hexagonal crystals

Silicate MineralsQuartz

Silicate MineralsLight silicates: Feldspar groupMost common mineral groupExhibit two directions of perfect cleavage at 90 degreesOrthoclase (potassium feldspar) and Plagioclase (sodium and calcium feldspar) are the two most common members

Potassium feldsparEuropean engineers use K-spar in highway aggregates to increase pavement reflectivity and wearing surface.

Plagioclase feldsparPlagioclase feldspars are components of decorative dimension stone, especially black granite (gabbro).

Common Silicate Minerals

Questions

Mineral groupsImportant nonsilicate mineralsTypically divided into classes based on anionsComprise only 8% of Earths crustOften occur as constituents in sedimentary rocks

Nonsilicate mineralsImportant nonsilicate mineralsMany nonsilicate minerals have economic valueExamplesHematite (oxide mined for iron ore)Halite (halide mined for salt)Sphalerite (sulfide mined for zinc ore)Native copper (native element mined for copper)

Native copper

Common Non-silicate Minerals

*******************Feldspars plagioklas adalah komponen batu dimensi hias, terutama "granit hitam" (gabro).******