random
-minerals are composed of atoms bonded together and are building blocks of rock
-rocks are composed of minerals and make up various geologic processes
minerals
must have following characteristics:
1. naturally occuring
2. solid
3.orderly crystalling sturcture
4. well-defined chemical composition
5. generally inorganic
naturally occuring
minerals form by naturally occurring geologic processes. Therefor diamonds and rubies sythetically created in labs are not minerals
solid
solid within temperate ranges normally experienced at earths surface. Thus, ice is considered a mineral, where liquid and vapor are not
orderly crystalline structure
atoms are arranged in an orderly, repetitive manner. reflected in the regularly shaped objects we call crystals. Some naturally occuring solids, like volcanic rock, lack this repetitive atomic structure
well-defined chemical compostition
most have compositions given by their chemical formula. In nature it is common for some atoms within a crystal structure to be replaced by others of similar size without changing the internal structure or properties. therefore, chemical comps of minerals
inorganic
inorganic solids found naturally in the ground. sugar, a crystalline solid like salt, but which comes from sugarcane or sugar beets, is a common example of such organic compounds. However, many marine animals secrete inorganic compounds, such as calcite,
rocks
-more loosely defined
-any solid mass of mineral, or mineral-like matter that occurs naturally as part of our planet
-some are made of one mineral, like limestone made up of
calcite
-some are aggregates of many minerals, such as granite
-some are composed
composition of minerals
-elements
-atoms
-atomic structure
elements
-basic building block of minerals
-less than 100 are known (92 naturally occurring)
-elements are organized by those with similar properties on the periodic table and given a two letter symbol
-also included is atomic number and masses
atoms
-smallest particle of matter that cannot be chemically split
-retains all characteristics of element
atomic structure of atoms
-central region is nucleus which consists of protons (+) and neutrons
-very dense particles almost identical in mass
-electrons (-) charged particles surrounding nucleus
-located in shells around nucleus and have negligible mass
-each shell holds a specif
atomic number (Z)
-equal to number of protons
-atoms with same number have same chemical and physical properties
-innermost shell holds max of 2 electrons
-others hold a max of 8
chemical bond
formation of compound by combining two or more elements. I transfer or sharing of electons that allows each atom to attain a full valence shell of electrons
-done when an atoms outermost shell does not contain
eight electrons to fill outer shell
ionic bonds
the attractions of oppositely charged ions to one another, producing an electrically neutral compound
-orderly arrangement of oppositely charged ions
-when one atom gives up one or more of its valence
electrons to form ions (positively and negatively char
covalent bonds
-a chemical bond formed by sharing of a pair of electrons between atoms (two hydrogen atoms)
-atoms share electrons to achieve electrical neutrality generally stronger
metallic bonds
-when valence electrons are free to move from one atom to another so that all atoms share the available valence electrons
-this is a weaker and less common bond
-found in copper, gold, aluminum, silver and brass
isotopes and radioactive decay
-isotopes=atoms of the same element with different masses
-same # of protons, different numbers of neutrons
-radioactive decay=nuclei of some atoms are unstable and change to become other isotopes of the same element or atoms of another element entirely
-
mass number
sum of neutrons and protons in an atom
-atoms of same element always have same number of protons, but neutrons can vary
structures of minerals
-minerals consist of an orderly array of atoms chemically bonded to form a particular crystalline structure
mineral groups - silicates
-most important group
-comprise most rock forming minerals
-very abundant group due to large percent of silicon and oxygen in earths crust
-quartz, hornblende, feldspar, biotite
silicon oxygen tetrahedron
-fundamental building block of silicate minerals
- 4 oxygen anions covalently bonded to a silicon cation
-not compound, complex ion with -4 charge
-form neutral compounds with addition of positive ions
-join in chain structure including double chains, she
important non-silicate minerals
-divided into classes based on anions
-comprise only 8% of earths crust
-occur as constituents in sedimentary rocks
-many have economic value
-carbonates, sulfates, and halides
carbonates
-primary constituent of limestone and dolostone
-calcite and dolomite are the two most important
-ex:hematite(iron ore), halite(salt), sphalerite(zinc ore), native copper
carbonates properties
-determined by observation of performing simple test
-several physical properties are used to identify hand samples of minerals
physical properties
-crystal form
-luster
-color
-streak
-hardness
-cleavage
-fracture
-specific gravity
-other
polymorphs
-minerals built with same composition but different crystalline structure
- diamonds and graphite because when pure they are both
made up of carbon atoms, yet they display drastically
different properties
-phase change is when one polymorph changes to ano
crystal form
external expression of minerals internal structure
-in halite, bonding of Na ions to Cl ions results in a cubic shape or form
optical properties
luster
ability to transmit light
color
streak
luster
appearance of mineral in reflected light
categories:-metallic
-non-metallic
metallic
-appearance of metals regardless of color
-some, such as are native copper and galena, develop a dull coating or tarnish when exposed to the atmosphere. because they are not as shiny as samples with freshly broken surfaces, these samples are often said to
non-metallic
-vitreous
-glassy/silky=satin cloth
-dull/earthy= like soil
-pearly=like a pearl or inside of clam shell
-greasy=coated in oil
color
-generally unreliable for mineral identification
-often highly variable due to slight changes in mineral chemistry
-exotic colorations of certain minerals produce gemstones
streak
-color of mineral in its powdered form
-made by rubbing mineral on unglazed porcelain, termed streak plate
-even though color varies, streak does not
mineral strength
tenacity
hardness
cleavage
fracture
hardness
-resistance to abrasion or scratching
-rubbing mineral of unknown hardness against one with known hardness
-one of the most useful properties
cleavage
-tenancy to break along specific planes of weak bonding
-produces flat, shiny surface
-described by resulting geometric shapes including number of planes and angle between planes
-not all minerals have this property
fracture
-absence of cleavage when a mineral is broken
-when minerals that have chemical bonds equally, or nearly equal, strong in all directions
-types: 1. irregular fracture = uneven surfaces
2.conchoidal fracture = smooth curved surfaces resembling broken glass
specific gravity
-weight of a mineral divided by the weight of an equal volume of water
-average value is 2.7
-density=mass/volume
other properties
magnetism, reaction to hydrochloric acis, malleability, double refraction, taste, smell, and ellasticity
aggregate
minerals are found together as a mixture in which the properties of the individual minerals are retained
principal mineral in glass
quartz(clear, conchoidal fracture, scratch glass)
cleavages
quartz=no cleavage(3-dim)
feldspars=two planes at 90(3 dim)
micas=one plane in sheets
hornblende=two planes at 60 and 120(double chains)
augite=two planes at right angles(single chain)
olivine=none(single tetrahedron)
non silicates in sedimentary rocks
calcite,dolomite, gypsum, halite
crystal shape
external expression of a minerals orderly internal arrangement of atoms
-differs from cleavage bc it is planes of
weakness along which the mineral breaks
fractional crystallization
crystallization of part of a magma, leaving behind a different comp from the original magma
-comp changes bc different elements crystalize at different rate, leaving behind more unused elements