Lab Activity on Minerals
B–43
B–44
Lab Activity on Minerals
Overall Color
ay
Gr
to
Mica
te
Whi
ink
or P
and er
e
l
th
bo
phi e (a no al )
m
A xen i ner
o
Pyr la ck m
b
Olivine
ck
Bl a
Gabbro
Granite
Quartz
Basalt
Rhyolite
Dark Gray
to Black
Mafic
(Low in Si)
Minerals in
The rocks
Names of
Rocks
Volcanic Rocks that contain no Minerals (They are made of disordered atoms, i.e. glass)
Obsidian: black, gray or red-brown; glassy. Contains no crystals. Usually has felsic composition.
Pumice: gray, full of holes, very lightweight, spun glass. Usually has felsic composition.
Special Textures of Some Volcanic Rocks (terms used as adjectives for the above rock names)
Porphyritic: a mixture of microscopic crystals and crystals large enough to see.
Vesicular: containing large rounded holes (frozen gas bubbles).
0%
25%
50%
75%
Intermediate
Feldspar
Cream, Pink and/or Light Gray
Composition
Most grains
Microscopic
All grains large
enough to see
100%
Felsic (High in Si)
Minerals in Igneous Rocks
Lab Activity on Minerals
B–45
B–46
Lab Activity on Minerals