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discovering ireland > worksheet 3 > Flashcards

worksheet 3 Flashcards

1
Q

what is a mineral

A

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

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2
Q

how are minerals formed

A

by geological processes

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3
Q

what properties are used to identify minerals

A

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

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4
Q

what are the options for transparency

A

transparent, translucent, opaque

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5
Q

how can color vary

A

based on mineral or within mineral of single type

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6
Q

what is luster

A

amount and quality of light reflected from mineral

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7
Q

what is most minerals luster

A

metallic, vitreous or dull

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8
Q

what does it mean if a mineral has a metallic luster

A

has the highest reflectivity (similar to metal)

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9
Q

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

A

slightly less bright than metal

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10
Q

what does it mean if a mineral has a vitreous luster

A

similar to broken glass

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11
Q

what does it mean if a mineral has a pearly luster

A

soft reflectance shown by some layer silicates

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12
Q

what does it mean if a mineral has a silky luster

A

soft reflectance that varies across tiny ridges within a specimen

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13
Q

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

A

least reflective

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14
Q

what is a cleavage

A

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

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15
Q

what is a fracture

A

when rocks break unevenly or conchoidally

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16
Q

what does conchoidal mean

A

a curvy break in rock

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17
Q

what is the scale of hardness

A

1-10, 10 is the hardest

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18
Q

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

A

~6, ~5, ~2.5

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19
Q

what is a mineral streak

A

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

20
Q

what is the habit of crystal

A

shape of the crystal when it grows unimpeded by other crystals

21
Q

how does habit help determine when minerals form

A

the earlier the mineral forms the more euhedral will be

22
Q

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

A

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

23
Q

what is specific density

A

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

24
Q

what does reacting the rock with dilute HCl tell you

A

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

25
Q

what does it mean if rocks deflect magnetic compass

A

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

26
Q

list the common rock forming minerals

A

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

27
Q

what is a solid solution

A

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

28
Q

how can quartz be identified

A

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

29
Q

how can feldspar be identified

A

white or pink, opaque, vitreous, two sets of cleavage, less hard than glass

pink –> orthoclase/potassium feldspar
striations –> plagioclase feldspar

30
Q

how can you identify micas

A

soft and split along single cleavage plane

muscovite –> silver/gray
bitotite –> black/brown

31
Q

how can you identify calcite

A

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

32
Q

what are the rock types

A

igneous, sedimentary, metamorphous

33
Q

what are igneous rocks

A

rocks formed from magma

34
Q

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

A

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

35
Q

what are sedimentary rocks

A

rocks formed by deposit and then undergoing pressure

36
Q

what are classic rocks

A

sedimentary rocks made by other rocks breaking up

37
Q

what are the different types of sedimentary classic rocks

A

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

38
Q

what are organic rocks

A

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

39
Q

what are metamorphic rocks

A

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

40
Q

what is thermal metamorphism

A

metamorphic rocks produced by increase in temperature

41
Q

what is dynamic metamorphism

A

metamorphic rocks produced by change in pressure

42
Q

what is regional metamorphism

A

metamorphic rocks produced by changed in both temperature and pressure.

occurs in large region often
can be low or high grade

43
Q

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

A

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)

44
Q

where do igneous rocks occur in ireland

A
  • northeast of ireland in antrim
  • southeast ireland (wicklow through kilkenny)
  • west of galway
  • in mourne mountains
45
Q

where do metamorphic rocks occur in ireland

A

donegal, mayo, galway

46
Q

what are some of the major unconformities in ireland

A
  • 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
47
Q

how do you identify unconformities on map

A

look for colors missing

discovering ireland (10 decks)

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