Igneous textures Flashcards
ophitic
An elongated mineral enclosed by another mineral.
Equigranular
When crystals in an igneous rock are of approximately the same size
cumulate
Igneous rocks are formed by the accumulation of crystals due to gravity settling and is typical of layered intrusions.
Amygdaloidal
where there are large vesicles that have been filled by secondary mineral.
Euhedral
Crystal are well formed with good crystal faces
Phenocryst
Large or conspicuous crystals in an igneous rock, much larger than the ground mass
Porphyritic
An igneous texture where large crystals, called phenocrysts, are completely surrounded by smaller crystals
Vesicular
A textural term used for a rock containing vesicles. Vesicles were bubbles of gas which came out of solution as a result of pressure release.
Flow banding
Occurs when layers of dark and light minerals form due to separation of minerals with a lava flow. Crystals are aligned parallel to the flow direction.
What rock does flow banding occur in?
Rhyolite
In what rocks would you see a porphyritic texture?
basalt, granite
In what rocks would you see an ophitic texture?
dolerite and gabbro. Plagioclase ‘laths’ are enclosed by augite
In what rocks would you see a vesicular texture?
basalt and pumice
In what rocks would you see and amygdaloidal texture?
basalt
In what rocks would you see flow banding?
Rhyolite
