Minerales y Rocas_3

7/28/2019 Minerales y Rocas_3

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Mafic

Mafic is used for silicate minerals, magmas, and rocks which are relatively

high in the heavier elements. The term is derived from using the MA from

magnesium and the FIC from the Latin word for iron, but mafic magmasalso are relatively enriched in calcium and sodium.

Igneous Rocks come in three basic varieties, mafic,intermediate, and felsic. Ultramaficrocks are lower in silica thaneven mafic rocks.

Ultramafic

Having very low silica content and very rich in Fe and Mg

Intermediate Igneous

Rocks that have a chemistry between mafic and felsic (silica amounts

between 53 to 65 %).

Felsic

Silicate minerals, magmas, and rocks which have a lower percentage of the

heavier elements, and are correspondingly enriched in the lighter elements,

such as silica and oxygen, aluminum, and potassium. The term comes from

FEL for feldspar (in this case the potassium-rich variety) and SIC, whichindicates the higher percentage of silica.


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Biotite Mica

insulation, electronics,

filler in plasterboard,

cement, paint, peels in

thin sheets

Muscovite Micainsulation, electronics,

filler in plasterboard,

cement, paint

peels in thin sheets

Calcite

the matrix in cement

(CaCO3), optical equipment

(#3 on Mohs scale of

hardness)

Quartz

glass, crystal, radios, watches,

computers, electronics, jewelry

(onyx, agate, & amethyst) (#7on Mohs scale)

Sulfur

matches, fireworks, medicine

(sulfa drugs), sulfuric acid,

vulcanization of rubber yellow

color, flammable, smells acrid

Graphite

pencil lead, dry lubricant,

batteries (hardness of #2)
http://www.cmdowns.com/images/minerals/biotite-mica.jpg


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Gypsum

drywall, plaster of Paris

(#2 on Mohs scale)

Plagioclase Feldsparabrasives, filler in paint and

plastics most common

minerals in igneous rocks

Orthoclase Feldsparabrasives, filler in paint and

plastics most common

minerals in igneous rocks

Hematite

iron ore, cabochon jewelry

(when polished)

Halite

table salt, manufacture of

soap, paper, petroleum &

glass tastes salty

Galena

lead ore for pipes, xray

shielding, fishing weights

very dense


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Magnetite

iron ore magnetic

Talc

talcum powder, paints,

ceramics, paper coatings

softest mineral

(#1 on Mohs scale)

Olivine

source of peridotite for

jewelry green color

Pyrite

sulfuric acid production

known as fools gold

Limonite

iron ore, yellow pigment for

paint adds color to soil

Barite

barium ore for gastrointestinal

x-rays, white pigment for paint


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Dolomite

lime for neutralizing acidic soil,

road aggregate, building stone

Bauxite

aluminum ore for soft drink

cans, softball bats, alloy

wheels, lawn furniture

Hornblende

common mineral in

igneous rocks

Copper

coins, pipes, wire, cooking

utensils, jewelry ductile,

malleable and conductive

Kaolinite

ceramics, china, pottery,

filler in paper

Chalcedony

arrowheads, driveway

gravel, ornamental stone,

cabochon jewelry
http://images.google.com/imgres?imgurl=http://www.okbu.edu/academics/natsci/naturalsci/mcwill/rocks/augite%2520(pyroxene).jpg&imgrefurl=http://www.okbu.edu/academics/natsci/naturalsci/mcwill/rocks/augite.html&h=220&w=288&sz=21&tbnid=uroaC6aGIlsJ:&tbnh=84&tbnw=110&start=19&prev=/images%3Fq%3Dpyroxene%26hl%3Den%26lr%3D%26safe%3Doff%26sa%3DN


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Augite (pyroxene)

is only of importance to

collectors, scientists

and petrologists

Diopside

has no industrial use,

good specimens can be

used as gemstones

Hypersthene

As mineral specimens

and there is an

ornamental variety

Amphibole

semiprecious gemstones; as

asbestos: fire proofing

materials, cement, brake pads,

plastics, paper products and

textiles

Ilmenite

As the major ore of titanium,

a minor ore of iron, as a flux

in blast furnaces, as an

abrasive

Kimberlite

diamond ore. Diamonds used

for jewelry, cutting tools,

polishing hard metal, bearings

for laboratory instruments
http://images.google.com/imgres?imgurl=http://www.okbu.edu/academics/natsci/naturalsci/mcwill/rocks/augite%2520(pyroxene).jpg&imgrefurl=http://www.okbu.edu/academics/natsci/naturalsci/mcwill/rocks/augite.html&h=220&w=288&sz=21&tbnid=uroaC6aGIlsJ:&tbnh=84&tbnw=110&start=19&prev=/images%3Fq%3Dpyroxene%26hl%3Den%26lr%3D%26safe%3Doff%26sa%3DN


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Feldspar is the most common rock-forming mineral (about 60% of the earths

crust). The mineral name feldspar is derived from the German words feld +

spar. The word "feld" is "field" in German and "spar" is a term for light colored

minerals that break with a smooth surface. Feldspar minerals are usuallywhite or very light in color, have a hardness of 6 on the Mohs Scale of

Hardness and perfect to good cleavage (plane of breakage) in two directions.

Feldspar is a common name that applies to a group of minerals with a generalchemical formula ofx Al(Al,Si)3O8, where x can be sodium (Na) and/or

calcium (Ca) and/or potassium (K).

Feldspar


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Why is feldspar important?The feldspars are a family of silicate minerals which occur in igneous rocks. Thereare many different members to the feldspar group. Obviously, silica and

oxygen form the foundation for the group, but calcium, sodium, andpotassium are also present. One of these elements is usually dominant, but

most of the feldspars contain all 3 in varying amounts. It is the proportions of these

3 elements which help determine which specific feldspar is formed. The feldsparsare divided into 2 broad categories: plagioclase, which contains calcium

and sodium; and orthoclase, which contains potassium.


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Plagioclase and Orthoclase

It is important to be able to distinguish

between plagioclase and orthoclase.. You

can make an educated guess in the field

based on several assumptions, and a feweasily identifiable physical features - color

and the presence (or absence) of "striations."

Striations are often visible on plagioclase,

and look like very fine (almost microscopic)

parallel lines cut into the face of a mineral

fragment. All feldspars which have striationsare plagioclase, but not all plagioclase has

striations. Only orthoclase can be pink,

and only plagioclase can be dark gray

to black. Unfortunately, both can be light in

color, and since most feldspars are nearly

white we're often still faced with a nastyidentification problem. If it's white and has

striations, I call it plagioclase. If it's white but

you can't see any striations, just call it

feldspar. The following graphic summarizes

the field identification of feldspar:


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A fine-grained, dark-colored rock of volcanic origin composed primarily

of plagioclase feldspar, and pyroxene, together with other minerals,

usually including olivine and ilmenite (an oxide of iron and titanium).

Basalt is the most common extrusive igneous rock on the terrestrial

planets and covers about 70% of Earths surface.

Basalt


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Any of a group of dark, dense, rock-forming silicate minerals rich in

calcium, iron, and magnesium and commonly found in basalt. The group

includes augite, hypersthene, and diopside, with composition varying as a

mixture of FeSiO3, MgSiO3, and CaSiO3. Pyroxenite is an igneous rockcomposed largely of pyroxene.

Pyroxene

Augite Hypersthene Diopside


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Amphibole is a name given to silicate minerals with the general composition

Ca2(Fe,Mg)5Si8O22(OH)2. The commonest form is hornblende; other speciesinclude anthophyllite, cummingtonite, tremolite, actinolite, riebeckite, and

glaucophane. A variety of jade, called nephrite, consists of actinolite in a finely

fibrous form.

Amphibole

Hornblende Nephrite (actinolite)


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Gabbro is a dark, coarse-grained,intrusive igneous rock chemically

equivalent to basalt. It is a plutonic rock,

formed when molten magma is trapped

beneath the Earth's surface and cools

slowly into a hard, coarsely crystalline

mass. It is dense, greenish or dark-colored

and contains varied percentages of

plagioclase feldspar, pyroxene, amphibole,

and olivine (called olivine gabbro when

olivine is present in large quantities).

Quartz gabbros are also known to occur

and are probably derived from magma that

was oversaturated with silica.

Gabbro

Plutonic rocks (also called

intrusive igneous rocks) arethose that have solidified below

ground.


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It is an igneous rock with extremely coarse grain size. To elaborate, a pegmatite

has the same base constituents as granite (quartz, feldspar, mica) except the

crystals are larger in size. In basic granite, the rock forming minerals usually

crystallize in sizes between 0.4 and 1 inch. In pegmatites, the minerals can

crystallize into larger sizes. It is not uncommon to find crystals over a meter inlength in larger pegmatites. Large pegmatites may extend from 5 to 100 feet

thick and 100 to 1000 feet in length. Crystals can grow to tremendous sizes, such

as quartz crystals 17 feet long and 8 feet in diameter, orthoclase crystals 33

feet by 33 feet, beryl 19 or more feet in length, tourmaline crystals 10 feet long and

mica sheets with up to 68 square feet of surface area.

Pegmatites

Molybdenite

Londonite

(Madagascar)


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Kimberlite is a mica peridotite

which occurs at Kimberley, South

Africa, the source of rich deposits

of diamonds. These diamonds were

originally found in decomposed

kimberlite which was colored yellow

by limonite, and so was called"yellow ground." Deeper

workings encountered less altered

rock, undecomposed kimberlite,which miners call "blue ground."

Kimberlite occurs in "kimberlite

pipes," vertical columns of rock that

rise from deep magma reservoirs.

Peridotite is a dense, coarse

grained ultrabasic rock,

consisting mainly of the minerals

olivine and pyroxene

Kimberlite


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Many rocks with an overall fine-grained texture display scattered minerals that

are clearly greater than 1 mm across. This combination of two crystal size

populations is called porphyritic.

Porphyritic Texture

It indicates that the magma sat and cooled a bit below the Earth's surface, thus

giving time for the large crystals to grow, and then it erupted onto the surface,which allowed the rest of the rock to cool very quickly. Porphyritic textures

thus indicate two-stage cooling histories.


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