MINERALOGY PT 1

Mineralogy

scientific study of minerals, structure (chemical and crystalline), properties (physical), processes (origin, formation and occurrence), classification and distribution, and uses

minerals

this are naturally occurring, inorganic, solid element or compound crystalline substances, has definite atomic structure and chemical composition;

over 4000 minerals exist in earth crust;

all are composed of oxygen, silicon, aluminum, iron, calcium, potassium, sodium, and magnesium

rock and ore forming minerals

2 classifications and mineral groups

rock forming minerals

minerals found in abundance of earth crust;

forms igneous, sedimentary, or metamorphic rocks

ore forming minerals

minerals that are of economic values;

limited mode of occurrence;

formed by more unusual processes

color, streak, lustre, structure and form (habit), hardness, specific gravity, cleavage. fracture, tenacity

physical properties of minerals (8)

color

not constant in most of the minerals; due to the stain or impurities in the minerals; may indicate that mineral has underground peculiar phenomena

play of colors

development of series of prismatic colors by turning about in light

change of colors

similar to play of colors but slower rotation

iridescence

show rainbow colors either in the interior or on the surface

streak

color of mineral powder; nearly constant than the color; determined by marking unglazed porcelain or simply by scratching with a knife and observing the powder color

lustre

description of how much a mineral reflects light

metallic/ shiny, nonmetallic/dull

2 under lustre

classy (vitreous)

under metallic/shiny luster; like broken glass

metallic

under metallic/shiny luster; like metal

pearly

under metallic/shiny luster; like pearls

structure and form (habit)

denotes the shape and form of minerals

prismatic

elongated in one direction like prism

tabular

tabular or plate like shape

equant

posses approximately same side length in every directions

foliated

thin sheets, flakes, or scales

hopper

edges are fully developed but interior spaces are not filled; hollow

plumose

fine, feathery scales resembling plumes

bladed

blade like structure, elongated, flat crystals like knife blades

fibrous

crystal aggregates resembling long, slender needles, hair or threadlike fibers

reticulated

aggregate of crystals forming a network or lattice

stellated

composed of branches which radiate star like from a central point

dendritic

divergent branching and treelike mineral growth

columnar/stalatitic

thick or thin column like structure

micaceous

thin, flat sheets or flakes that easily peels or split off a larger mass

acicular

contains many long, slender crystals which may radiate like needles or bristles from common base; long narrow like pine leaf

filiform

exhibits many hair like or threadlike filaments

radiated

fibrous diverging from central points

lamellar

made of separable plates; feathery or delicate aggregates

colloform

spherical, rounded, or bulbous shape

botryoidal, reniform, mamillary

under colloform (3)

botryoidal

an aggregate-like bunch of grapes or globular

reniform

kidney shaped aggregate

mamillary

display soft, rounded curves

striated

display shallow parallel grooves or lines along flat crystal faces

granular

densely packed grains

massive

no definite shape for minerals; large and lumpy

specific gravity

the density of the mineral compared to the density of water

high

metallic minerals have _ SG

lower

non-metallic minerals have _ SG

cleavage

tendency of a crystallized mineral to break along certain definite planes yielding more or less smooth surface

cubic

3 cleavages

octahedral

4 cleavages

dodecahedral

6 cleavage

basal

1 cleavage

fracture

defined as the appearance of its broken surface

conchoidal

concentric rings or curved surface

even

smooth and flat

uneven

irregular surface

splintery

breaks with a rough

tenacity

behavior of mineral when deformed or broken

sectility

minerals may be cut with a knife

malleability

the mineral may be pounded out into thin sheets

brittleness

the mineral breaks or powders easily

elasticity

regains former shape as pressure is released

ductility

mineral may be drawn into a wire; tough as well

plasticity

mineral will not go back to original position when released

crystallography

the science concerned with the formation, properties, and structure of crystals; delas with the geometric forms of crystals

mineral crystal system

also called mineral habits; refers to the way crystals form within a specific mineral

crystal forms

internal atomic arrangement of mineral manifested outwardly by development of geometrical shapes or crystal characters

crystallized, amorphous, crystalline

3 types of crystal form

crystallized

mineral occurs in the form of well-defined crystals

amorphous

shows absolutely no signs or evidence of crystallization

crystalline

well-defined crystals are absent but a tendency towards crystallization is present

symmetry

described the repetition of structural features

translational, point

2 general types of symmetry

translational

periodic repetition of structural feature across a length or through an area or volume

point

periodic repetition of structural feature at a point; reflection, rotation, and inversion are examples of point symmetry

lattices

directly related to translational symmetry; a network or array composed of single motif that has been translated and repeated at fixed intervals throughout the space

Bravais lattice

there are only 14 different lattices that may be formed in a 3D space; divided into 6 crystal systems

primitive, face centered, body centered

3 types of bravais lattice

crystal systems

all minerals form crystals in one of the systems and are defined by a combination of 3 factors

number of axis, length of axis, angles the axes meet

3 factors under crystal systems

isometric, tetragonal, orthorhombic, monoclinic, triclinic, hexagonal

6 crystal systems

isometric system

also called cubic system

number of axis: 3

length of axis: equal length

angles: intersect at 90

has the highest degree of symmetry among all crystal systems; singly refractive or isotropic due to equality of axes

tetragonal system

number of axis: 3

length of axis: axis C is longer; axis A and B are equal length

angles: intersect at 90

examples: apophyllite, idocrase, rutile, scapolite, wulfenite, zircon

orthorhombic systems

number of axis: 3

length of axis: all axis are of different lengths

angles: intersect at 90

generally has 3 symmetry classes, may include another one; highest symmetry available is 2 fold

monoclinic system

number of axis: 3

length of axis: different lengths

angles: axis A and C may intersect at 90; axis B intersects at an oblique angle