Download Rock Texture Chart

Texture
Description
Examples
Formation
Vesicular
Non-Crystalline
Fine (Aphanitic)
Air bubbles/gas pockets
Glassy texture, no crystals formed
If the sample is held at arm’s length, you cannot distinguish
individual grains or crystals. Grains smaller than the thickness of
your fingernail.
If the sample is held at arm’s length you can see distinct grain
sizes. Grain sizes range from thickness of a fingernail, to the
width of your nail bed. Could be described as “speckled.”
Large grain sizes can be seen, the size of the tip of your finger
and larger.
Two different sizes of grain are visible. Usually a fine grain (ash)
with larger, angular or rounded fragments visible
Looks and feels like dirt, clay, rock or sand particles pressed
together over time.
Scoria, pumice
Obsidian
Rhyolite, andesite,
basalt
Igneous
Igneous
Igneous
Granite, Diorite,
Gabbro, Dunnite
Igneous
Pegmatite
Igneous
Rhyolite, andesite,
basalt
Conglomerate,
sandstone, shale,
mudstone, arkose,
breccia , claystone
Limestone, dolostone,
chert, dolostone, rock
salt, rock gypsum
Coal, limestone, chalk,
coquina
Igneous
Coarse
(Phaneritic)
Very Coarse
Porphyritic
Clastic
Non-Clastic or
Chemical
Crystal structure derived from minerals precipitating out of
solution to form rocks.
Biologic
Organic materials pressed together over time
Foliated
A layered or banded appearance that is produced by exposure to Schist, slate, gneiss
heat and directed pressure
Results from a recrystallization of existing material, there are no Quartzite, hornfels,
bands or layers visible
marble
Non-Foliated
Sedimentary
Sedimentary
Sedimentary
Metamorphic
Metamorphic