Igneous Rocks Flashcards
1
Q
most important mineral in igneous rocks
A
SiO2
- 50% silica content in basalt
- up to 75% silica in granatic samples
2
Q
dykes
A
cut across rock samples
3
Q
sills
A
follow bedding layers
4
Q
Hypabyssal
A
used to describe dykes and sills
5
Q
How are igneous rocks formed?
A
formed from the cooling and solidification of magma or lava emplaces on or within the earths crust
6
Q
Basaltic Lava
A
formed at 1250C
- volcanic, fine-grained
7
Q
what is ropey lava called?
A
pa hoe hoe
8
Q
Silicates of Igneous Rocks (7)
A
- olivine
- pyroxene
- amphibole
- mica
- feldspar
- feldspathoid
- quartz
9
Q
non-silicates of Igneous Rocks (1)
A
opaque minerals [carbonates]
10
Q
Accessory minerals of Igneous Rocks (3)
A
apatite
titanite
zircon
11
Q
difference between olivine and pyroxene
A
Cleavage: olivine has no cleavage
Twinning: pyroxene
12
Q
Difference between Amphibole and Pyroxene
A
Amphibole - has cleavages parallel to long edges
Pyroxene - has cleavage parallel to short edges of crystal
