worksheet 3

Question 1

what is a mineral

Answer 1

naturally occurring substance made of inorganic chemical compounds (meaning that atoms have >1 element)

Question 2

how are minerals formed

Answer 2

by geological processes

Question 3

what properties are used to identify minerals

Answer 3

color, transparency, luster, cleavage and fracture, hardness, streak, habit, specific gravity, reaction with HCl, deflection of magnetic compass,

Question 4

what are the options for transparency

Answer 4

transparent, translucent, opaque

Question 5

how can color vary

Answer 5

based on mineral or within mineral of single type

Question 6

what is luster

Answer 6

amount and quality of light reflected from mineral

Question 7

what is most minerals luster

Answer 7

metallic, vitreous or dull

Question 8

what does it mean if a mineral has a metallic luster

Answer 8

has the highest reflectivity (similar to metal)

Question 9

what does it mean if a mineral has a sub-metallic luster

Answer 9

slightly less bright than metal

Question 10

what does it mean if a mineral has a vitreous luster

Answer 10

similar to broken glass

Question 11

what does it mean if a mineral has a pearly luster

Answer 11

soft reflectance shown by some layer silicates

Question 12

what does it mean if a mineral has a silky luster

Answer 12

soft reflectance that varies across tiny ridges within a specimen

Question 13

what does it mean if a mineral has a dull/earthy luster

Answer 13

least reflective

Question 14

what is a cleavage

Answer 14

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

Question 15

what is a fracture

Answer 15

when rocks break unevenly or conchoidally

Question 16

what does conchoidal mean

Answer 16

a curvy break in rock

Question 17

what is the scale of hardness

Answer 17

1-10, 10 is the hardest

Question 18

what is the hardness of glass plate, steel and a finger nail

Answer 18

~6, ~5, ~2.5

Question 19

what is a mineral streak

Answer 19

a powder version of the mineral left that is a specific color that is left when you rub the mineral against a specific plate

Question 20

what is the habit of crystal

Answer 20

shape of the crystal when it grows unimpeded by other crystals

Question 21

how does habit help determine when minerals form

Answer 21

the earlier the mineral forms the more euhedral will be

Question 22

what are the options for habit in terms of quality of shape

Answer 22

euhedral –> nice crystal shape
subhedral –> meh crystal shape
anhedral –> no real crystal shape

Question 23

what is specific density

Answer 23

density related to water. if sg is 3, then density is 3 times greater than water. no units

Question 24

what does reacting the rock with dilute HCl tell you

Answer 24

if there are carbonate minerals in the rock (dolomite reacts less than calcite does but still does react)

Question 25

what does it mean if rocks deflect magnetic compass

Answer 25

if rocks deflect magnetic compass then know that there is iron or magnetite

Question 26

list the common rock forming minerals

Answer 26

quartz, orthoclase feldspar, plagioclase feldspar, biotite mica, muscovite mica, calcite

Question 27

what is a solid solution

Answer 27

a family of materials with range of compositions but a single crystal structure (aka the exact element changes but the structure is the same)

Question 28

how can quartz be identified

Answer 28

hard, glass-like luster, lack of cleavage, conchoidal fracture, chemically unreactive

Question 29

how can feldspar be identified

Answer 29

white or pink, opaque, vitreous, two sets of cleavage, less hard than glass pink --> orthoclase/potassium feldspar striations --> plagioclase feldspar

Question 30

how can you identify micas

Answer 30

soft and split along single cleavage plane muscovite --> silver/gray bitotite --> black/brown

Question 31

how can you identify calcite

Answer 31

looks similar but softer than quartz, 3 sets of cleavage, reacts with HCl

Question 32

what are the rock types

Answer 32

igneous, sedimentary, metamorphous

Question 33

what are igneous rocks

Answer 33

rocks formed from magma

Question 34

what is the difference between acid/felsic and basic/malic igenous rocks

Answer 34

acid --> rich in quartz basic --> rich in iron and magnesium

Question 35

what are sedimentary rocks

Answer 35

rocks formed by deposit and then undergoing pressure

Question 36

what are classic rocks

Answer 36

sedimentary rocks made by other rocks breaking up

Question 37

what are the different types of sedimentary classic rocks

Answer 37

in order of biggest to smallest grain size: conglomerates/breccias, sandstone, siltstone, shale/mudstone

Question 38

what are organic rocks

Answer 38

made of organic molecules like fossils and minerals (calcite, dolomite, carbon)

Question 39

what are metamorphic rocks

Answer 39

rocks that were igneous or sedimentary and then got changed by heat or pressure

Question 40

what is thermal metamorphism

Answer 40

metamorphic rocks produced by increase in temperature

Question 41

what is dynamic metamorphism

Answer 41

metamorphic rocks produced by change in pressure

Question 42

what is regional metamorphism

Answer 42

metamorphic rocks produced by changed in both temperature and pressure. occurs in large region often can be low or high grade

Question 43

what are the main types and ages of rock that form irelands bedrock

Answer 43

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)

Question 44

where do igneous rocks occur in ireland

Answer 44

- northeast of ireland in antrim - southeast ireland (wicklow through kilkenny) - west of galway - in mourne mountains

Question 45

where do metamorphic rocks occur in ireland

Answer 45

donegal, mayo, galway

Question 46

what are some of the major unconformities in ireland

Answer 46

- 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

Question 47

how do you identify unconformities on map

Answer 47

look for colors missing