-
Home
| Where
to Find
Rocks | Field
Equipment | Home
Tools | Organise
Your Collection | Storage
and Display | Field
Safety | Blog
Igneous Rock Classification
There are a few different types
of igneous rock classification.
They have been named on the basis of different characteristics such as chemical composition, mineral content, texture, even geographical locality.
The historical nomenclature for igneous rocks is therefore confusing.
Nowadays, they are classified on the basis of mineralogy and sometimes texture.
Mineralogical
Classification
Mineralogy, and
particularly composition, tell us about the original
magma and how it evolved. Rocks that contain mainly dark,
ferromagnesian minerals such as
pyroxenes and olivine are mafic.
Rocks that contain mainly light, silica-rich minerals such as quartz
and feldspars are felsic.
The IUGS
Classification System is based on what minerals are found in
a rock.Textural Classification
Texture of a rock tells us about the environment in which the rock was formed and the cooling rate.Glassy texture indicates a very quick cooling rate. Silica-rich, felsic rocks can form glassy texture easier than mafic rocks, however there are mafic rocks that do it too. Rocks with glassy texture include obsidian, pumice, tachylite and scoria.
Crystalline textures show different types of grain size. Those are classified as coarse-grained, medium size, and fiine-grained. The larger the mineral grains, the slower was cooling of magma at the time when the minerals formed. This is a large group of rocks that contains granite, rhyolite, basalt, gabbro, and many, many others - the vast majority of all igneous rocks.
Fragmental textures are formed in the air from volcanic debris and ash. These include hyaloclasite, volcanic breccia and pyroclastic rocks such as tuff.
Custom Search
What's New
About Us
About Using Content
PHOTOS
MAKE MONEY BUYING AND SELLING GOLD!
CRYSTAL HEALING
[?] Subscribe To This Site
Home | Site Map | Site Search | Site Policies | About Us | Contact Us
This site uses British English, which is the English we use in Australia.
Disclaimer:
Although
best efforts have been made to ensure that
all the information on this
site is correct,
collecting-rocks-and-minerals.com is not to be blamed should there be a
mistake.
Copyright notice:
All contents of this website are strictly protected
by the Law of
Copyright. What does that
mean?
Copyright 2010-2021 collecting-rocks-and-minerals.com. ALL RIGHTS RESERVED.