Igneous Rocks
Part of Hall of Planet Earth.
![Igneous rocks](/var/ezflow_site/storage/images/media/amnh/images/exhibitions/permanent-exhibitions/rose-center-for-earth-and-space/hall-of-planet-earth2/igneous-rocks/1019453-1-eng-US/igneous-rocks_wideexact_2460.jpg 2460w,/var/ezflow_site/storage/images/media/amnh/images/exhibitions/permanent-exhibitions/rose-center-for-earth-and-space/hall-of-planet-earth2/igneous-rocks/1019453-1-eng-US/igneous-rocks_wideexact_1230.jpg 1230w,/var/ezflow_site/storage/images/media/amnh/images/exhibitions/permanent-exhibitions/rose-center-for-earth-and-space/hall-of-planet-earth2/igneous-rocks/1019453-1-eng-US/igneous-rocks_wideexact_800.jpg 800w,/var/ezflow_site/storage/images/media/amnh/images/exhibitions/permanent-exhibitions/rose-center-for-earth-and-space/hall-of-planet-earth2/igneous-rocks/1019453-1-eng-US/igneous-rocks_wideexact_400.jpg 400w)
Igneous rocks solidify from molten rock (called magma within the Earth and lava on the surface). They are identified by mineral content and texture — the size and shape of their mineral grains.
Texture is controlled by the rate of cooling: magma that cools slowly deep in the Earth forms rock with large crystals, and lava that cools quickly on the surface forms fine-grained rock.
In This Section
![Granite pegmatite_HERO](/var/ezflow_site/storage/images/media/amnh/images/exhibitions/permanent-exhibitions/rose-center-for-earth-and-space/hall-of-planet-earth2/hope-hero-images/granite-pegmatite_hero/1039641-1-eng-US/granite-pegmatite_hero_wideexact_1230.jpg 1230w,/var/ezflow_site/storage/images/media/amnh/images/exhibitions/permanent-exhibitions/rose-center-for-earth-and-space/hall-of-planet-earth2/hope-hero-images/granite-pegmatite_hero/1039641-1-eng-US/granite-pegmatite_hero_wideexact_800.jpg 800w,/var/ezflow_site/storage/images/media/amnh/images/exhibitions/permanent-exhibitions/rose-center-for-earth-and-space/hall-of-planet-earth2/hope-hero-images/granite-pegmatite_hero/1039641-1-eng-US/granite-pegmatite_hero_wideexact_400.jpg 400w)
Granite Pegmatite
This rock formed deep in the crust, near the top of a crystallizing magma chamber. It is composed of the minerals quartz (gray), orthoclase (pink), albite (white), and mica (dark and platy). The larger crystals grew more slowly than the smaller crystals.
![Diabase](/var/ezflow_site/storage/images/media/amnh/images/exhibitions/permanent-exhibitions/rose-center-for-earth-and-space/hall-of-planet-earth2/diabase/1022910-2-eng-US/diabase_wideexact_1230.jpg 1230w,/var/ezflow_site/storage/images/media/amnh/images/exhibitions/permanent-exhibitions/rose-center-for-earth-and-space/hall-of-planet-earth2/diabase/1022910-2-eng-US/diabase_wideexact_800.jpg 800w,/var/ezflow_site/storage/images/media/amnh/images/exhibitions/permanent-exhibitions/rose-center-for-earth-and-space/hall-of-planet-earth2/diabase/1022910-2-eng-US/diabase_wideexact_400.jpg 400w)
Diabase
This rock solidified from a basaltic magma within a few hundred meters of the surface, probably beneath a volcano. It cooled rapidly, giving it a fine-grained, peppery appearance. The black mineral is pyroxene, and the white one is plagioclase.
Donated by TILICON, Haverstraw, New York.
![Diorite](/var/ezflow_site/storage/images/media/amnh/images/exhibitions/permanent-exhibitions/rose-center-for-earth-and-space/hall-of-planet-earth2/diorite/1022920-2-eng-US/diorite_wideexact_1230.jpg 1230w,/var/ezflow_site/storage/images/media/amnh/images/exhibitions/permanent-exhibitions/rose-center-for-earth-and-space/hall-of-planet-earth2/diorite/1022920-2-eng-US/diorite_wideexact_800.jpg 800w,/var/ezflow_site/storage/images/media/amnh/images/exhibitions/permanent-exhibitions/rose-center-for-earth-and-space/hall-of-planet-earth2/diorite/1022920-2-eng-US/diorite_wideexact_400.jpg 400w)
Diorite
This rock crystallized in a mountain belt. It contains the minerals plagioclase (white) and hornblende (black).
Donated by New England Stone Industries, Inc., Esmond, Rhode Island.