worksheet 3 Flashcards
what is a mineral
naturally occurring substance made of inorganic chemical compounds (meaning that atoms have >1 element)
how are minerals formed
by geological processes
what properties are used to identify minerals
color, transparency, luster, cleavage and fracture, hardness, streak, habit, specific gravity, reaction with HCl, deflection of magnetic compass,
what are the options for transparency
transparent, translucent, opaque
how can color vary
based on mineral or within mineral of single type
what is luster
amount and quality of light reflected from mineral
what is most minerals luster
metallic, vitreous or dull
what does it mean if a mineral has a metallic luster
has the highest reflectivity (similar to metal)
what does it mean if a mineral has a sub-metallic luster
slightly less bright than metal
what does it mean if a mineral has a vitreous luster
similar to broken glass
what does it mean if a mineral has a pearly luster
soft reflectance shown by some layer silicates
what does it mean if a mineral has a silky luster
soft reflectance that varies across tiny ridges within a specimen
what does it mean if a mineral has a dull/earthy luster
least reflective
what is a cleavage
a line of weakness (crystallographic plane) alone which the mineral breaks easy. occurs due to the way that the elements are organized.
number of cleavage directions and the angles are used to help identify mineral
what is a fracture
when rocks break unevenly or conchoidally
what does conchoidal mean
a curvy break in rock
what is the scale of hardness
1-10, 10 is the hardest
what is the hardness of glass plate, steel and a finger nail
~6, ~5, ~2.5
what is a mineral streak
a powder version of the mineral left that is a specific color that is left when you rub the mineral against a specific plate
what is the habit of crystal
shape of the crystal when it grows unimpeded by other crystals
how does habit help determine when minerals form
the earlier the mineral forms the more euhedral will be
what are the options for habit in terms of quality of shape
euhedral –> nice crystal shape
subhedral –> meh crystal shape
anhedral –> no real crystal shape
what is specific density
density related to water. if sg is 3, then density is 3 times greater than water. no units
what does reacting the rock with dilute HCl tell you
if there are carbonate minerals in the rock (dolomite reacts less than calcite does but still does react)
what does it mean if rocks deflect magnetic compass
if rocks deflect magnetic compass then know that there is iron or magnetite
list the common rock forming minerals
quartz, orthoclase feldspar, plagioclase feldspar, biotite mica, muscovite mica, calcite
what is a solid solution
a family of materials with range of compositions but a single crystal structure (aka the exact element changes but the structure is the same)
how can quartz be identified
hard, glass-like luster, lack of cleavage, conchoidal fracture, chemically unreactive
how can feldspar be identified
white or pink, opaque, vitreous, two sets of cleavage, less hard than glass
pink –> orthoclase/potassium feldspar
striations –> plagioclase feldspar
how can you identify micas
soft and split along single cleavage plane
muscovite –> silver/gray
bitotite –> black/brown
how can you identify calcite
looks similar but softer than quartz, 3 sets of cleavage, reacts with HCl
what are the rock types
igneous, sedimentary, metamorphous
what are igneous rocks
rocks formed from magma
what is the difference between acid/felsic and basic/malic igenous rocks
acid –> rich in quartz
basic –> rich in iron and magnesium
what are sedimentary rocks
rocks formed by deposit and then undergoing pressure
what are classic rocks
sedimentary rocks made by other rocks breaking up
what are the different types of sedimentary classic rocks
in order of biggest to smallest grain size: conglomerates/breccias, sandstone, siltstone, shale/mudstone
what are organic rocks
made of organic molecules like fossils and minerals (calcite, dolomite, carbon)
what are metamorphic rocks
rocks that were igneous or sedimentary and then got changed by heat or pressure
what is thermal metamorphism
metamorphic rocks produced by increase in temperature
what is dynamic metamorphism
metamorphic rocks produced by change in pressure
what is regional metamorphism
metamorphic rocks produced by changed in both temperature and pressure.
occurs in large region often
can be low or high grade
what are the main types and ages of rock that form irelands bedrock
mainly from carboniferous age (300-350 mya), but does have some mesozoic or tertiary aged stratigraphy
mainly sedimentary rocks. carbonate rocks (limestones and dolomites are ~40% of ireland)
where do igneous rocks occur in ireland
- northeast of ireland in antrim
- southeast ireland (wicklow through kilkenny)
- west of galway
- in mourne mountains
where do metamorphic rocks occur in ireland
donegal, mayo, galway
what are some of the major unconformities in ireland
- precambrian-carboniferous unconformity (donegal, mayo, galway): 191 my
- ordovician-carboniferous (mayo, cavan, monaghan): 86 my
- silurian-carbonigerous (mayo, meath): 56 my
ordovician-devonian (waterford): 30 my
how do you identify unconformities on map
look for colors missing
