Igneous Rocks – Formed by the cooling and hardening of
melted rock.
There are two main types of igneous rock determined by
the cooling process.
Intrusive – rocks that form inside the earth due to magma
cooling slowly producing a large crystal texture
EX. Granite, Gabbro
Extrusive – rocks that form on the surface of the earth
producing small crystals due to rapid cooling of lava
EX. Basalt
 Obsidian - extrusive lava rock that cools extremely
fast producing a glassy appearance without crystals
 Pumice – extrusive sponge-like rock with pores due to
trapped gases during rapid cooling of lava
Rock Families
 This is a grouping of igneous rocks determined by
mineral composition (certain minerals re-crystallize at
certain temperatures – This is independent of speed of
cooling
Olivine ---- Augite --- Hornblend ---Mica-----Quartz
(Magnesium single chains (double chains) (sheets) (network)
Iron mineral
Feldspar
Rock Families
1) Mafic –Made of minerals that recrystalize first
containing Magnesium and iron (Fe)
Dark in color from the iron
EX. Intrusive - Gabbro
Extrusive - Basalt
2) Intermediate – Second to recrystallize and are medium in
color between dark and light
EX. Intrusive – Diorite
Extrusive – Andesite
3) Felsic - Last mineral to recrystallize form these rocks.
Light in color from the feldspar and quartz (SiO2)
EX. Intrusive - Granite
Extrusive – Rhyolite and Obsidian
Igneous Rocks – Formed by the cooling and hardening of melted rock.
There are two main types of igneous rock determined by the cooling process.
Intrusive –
EX.
Extrusive –
EX.
Rock Families
 This is a grouping of igneous rocks determined by mineral
composition (certain minerals re-crystallize at certain temperatures –
This is independent of speed of cooling
Olivine ---- Augite --- Hornblend ---Mica-----Quartz
(Magnesium single chains
(double chains) (sheets)
(network)
Iron mineral
Feldspar
Rock Families
1) Mafic –Made of minerals that recrystalize first containing Magnesium
and iron (Fe)
Dark in color from the iron
EX. Intrusive Extrusive -
2) Intermediate – Second to recrystallize and are medium in color between
dark and light
EX. Intrusive –
Extrusive –
3) Felsic - Last mineral to recrystallize form these rocks. Light in color from
the feldspar and quartz (SiO2)
EX. Intrusive Extrusive –