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Rock Identification Test > Framework/tectosillicates > Flashcards

Framework/tectosillicates Flashcards

1
Q

What are the main rock groups present within the framework/tectosillicate group?

A

Quartz, feldspar, feldspathoids, zeolites

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2
Q

What is the typical hardness of feldspar?

A

6/6.5

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3
Q

What type of twinning is common in feldspar minerals?

A

Perthite twinning where albite (a form of plagioclase) intergrows in fine lamella within k feldspar

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4
Q

Describe the cleavage of k and plagioclase feldspars

A

Two perfect/good cleavage directions supposed to intersect at near 90 degrees

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5
Q

Nepheline is an example feldspathoid. It commonly resembles quartz, but what three factors allow it to be distinguished?

A
  1. Hardness 5/6 when compared to quartz 7
  2. Greasy lustre when compared to quartz typical vitreous
  3. Has one cleavage plane- QUARTZ DOES NOT
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6
Q

What factor separates quartz from all other framework/tectosillicates?

A

NO CLEAVAGE

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7
Q

What are the three feldpathoids you need to identify?

A

Nepheline, sodalite, leucite

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8
Q

leucite appears similar to which zeolite? how can you distinguish the two?

A

analcime. honestly can seem to find valid ways to ditinguish between them

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9
Q

identify the follwing feldspathoid mineral:
Habit:
- football/hexagonal crystal shape when visible
hardness:
- 5/6 (scratched by qhartz glass)
lustre:
- typically vitreous
cleavage:
- one poorly formed direction might be visible
colour:
- typically white but could be others due to impurities
streak colour:
-white/non-visible

A

Leucite- the distinguishing thing will be the sorta ball shaped/hexagonal cleavage direction

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10
Q

Nepheline and quartz appear VERY similar to one another, how can you distinguish between the two?

A

nepheline is softer (hardness 5/6 vs 7) and has a poorly formed cleavage direction - quartz has conchoidal fracturing

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11
Q

state the key physical properties of sodalite

A 
habit:
- prismatic/isometric grains 
colour:
- bright blue colour, but darker than that of lazurite 
streak colour:
- typically no streak colour 
hardness:
- 5/6 (scratched by quartz glass)
lustre:
- can range from vitrous to greasy
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12
Q

what are the key diagnostic properties that separate lazurite, nepheline and leucite from one another and other minerals? (these are all felsdpathoids)

A

sodalite:
- has a distinct blue colour, common vitreous lustre and hardness 5/6
Leucite:
the football shaped aggregates (in the lab sample you can see it clearly its a plain brow rock with white circular crystals in it). It also has one potwential cleavage direction
nepheline:
- the habit is different to leucite (commonly isometric) and has a cleave direction and hardness 5/6

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13
Q

what is the most common sodalite?

A

lazurite

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14
Q

name the key zeolites that we have specimines for and thus need to be able to identify

A
  1. Scolecite
  2. Mesolite
  3. Thomsonite
  4. Chazabite
  5. stillbite
  6. Heulandite
  7. Analcime
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15
Q

a zeolite has the following properties, identify it:
habit:
- isometric football/hexagonal shaped crystals
colour:
white. no streak
lustre:
- commonly vitreous
cleavage:
- has one really poor cleavage direction
hardness:
-3/4 (scratched by steel nail)

A

analcime

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16
Q

how can you distinguish anaclime from other zeolites?

A

its isometric/cubic/hexagonal crystal habit

17
Q

what is the diangostic feature of stillbite and which group does it belong to?

A

a weird bow tie shaped crystal habit - belongs to the zeolite group

18
Q 
which zeolite can be idnetified from the following properties?:
habit:
- elongated/cubic 
- one good cleavage direction
-hardness 3/4
vitreous lustre
A

heulandite

19
Q

state the general physical properties of heulandite

A 
habit:
-elongated/cubic 
colour:
white/pink
lustre:
-vitreous 
hardness:
- 3/4
cleavage: 
one good cleavage direction
20
Q

scoloectie and mesolite are BOTH zeolites with radial aggregation and acicular crystal habits. how can you tell the difference?

A

the crystals are so fibrous in mesolite that they cna at times not even be visible, and in the class specimines there is a defintie difference between the size- mesolite crystals ar ebigger (look back on the document)

21
Q

which of the zeolites give acicular/fibrous crystals?

A
  • scolecite
  • mesolite
  • Thomsonite
22
Q 
the physical properties describe which zeolite?:
habit:
acicular 
aggregation: 
radial
colour:
white, no streak
hardness:
3/4
lustre:
vitreous 
cleavage:
one direction (between the crystals)
A

scolecite

23
Q 
the follwing properties describe which mineral? 
habit: 
- fibrous 
aggregation:
- radial
colour:
- white/no streak
Lustre:
- vitreous 
hardness: 1-2 (scratched by finger nails)
cleavage: one direction
A

mesolite

24
Q

what are the diagnostic properties of mesolite and what group does it belong to?

A
  • hardness is only 1/2 and the habits are very fibrous with radial aggregation
25
Q 
which zeolite can you indeitfy from the follwing properties?
Habit:
isometric- weird ball shaped aggregation but not similar to analcime 
colour: 
- white/pink
hardness: 
- 3/4
cleavage:
- one direction 
lustre:
- vitreous
A

Stillbite

26
Q

stae the physical properties of chazabite and which group it belongs to

A 
habit:
- cubic 
aggregation 
- granualr 
colour
- white/ no streak
lustre: 
-vitreous 
hardness:
- 3/4 scratched by steel nail 
cleavage: 
- one very poor direction
27
Q

how can you distinguish chazabite from other zeolites (considering they share A LOT of properties)

A
  • it is the only zeolite sample with a very clear cubic habit (the rest have a isometric ball/hexagonal shaped habits)
28
Q

which of the zeolite samples have a block/granular crystal shape?

A

chazabite and analcime

29
Q

which of the zeolite samples has platy/tabular/isometric habits?

A

heulandite, Thomsonite, stillbite

Rock Identification Test (14 decks)

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