Igneous rocks are the solidified products of molten rock — magma beneath the surface or lava at the surface. They form when molten material cools and crystallizes, producing textures and mineral assemblages that record cooling rate, composition and environment of formation. In everyday language you might hear "volcanic rocks," "lava rocks called" this or that, or simply "granite" and "basalt" — all are igneous in origin.
Origin: derived from magma (underground) or lava (extruded at the surface).
Primary mineral constituents: quartz, feldspars (plagioclase and K-feldspar), pyroxene, amphibole, olivine, biotite.
Key classification factors: texture (grain size), chemical composition (felsic to ultramafic), and mode of emplacement (intrusive vs extrusive).
How Igneous Rocks Form: Magma, Lava and Crystallization
Igneous processes are governed by temperature, pressure, volatiles and composition. Typical crystallization temperatures vary: basaltic magmas crystallize roughly between 1,000–1,200
Frequently Asked Questions
What is the main difference between igneous and volcanic rocks?
Volcanic rocks are a subset of igneous rocks formed by lava at or near the surface (rapid cooling). "Igneous" includes both volcanic (extrusive) and plutonic (intrusive) rocks like granite.
What are lava rocks called?
Commonly called basalt, scoria, pumice or obsidian depending on composition and texture; terms like pahoehoe and aa describe basaltic lava flow textures.
How can I tell granite from basalt in the field?
Granite is light-colored, coarse-grained with visible quartz and feldspar; basalt is dark, fine-grained, denser and may show vesicles or flow textures.
Are any igneous rocks dangerous or toxic?
Most are chemically inert, but ultramafic rocks can weather to asbestos minerals; avoid inhaling dust and wear protection when cutting samples. Fresh volcanic deposits may also pose heat and gas hazards.
What are the three types of meteorites?
The three broad categories are stony (chondrites/achondrites), iron (Fe-Ni metal), and stony-iron (pallasites and mesosiderites).
Can Orvik identify my igneous rock photos?
Yes. Orvik uses image recognition and curated datasets to suggest identifications and similar specimens — always verify with field notes and, if needed, lab tests.
Where are igneous rocks commonly found?
At plate boundaries and hotspots: mid-ocean ridges (basalt), subduction zones (andesite/rhyolite), continental batholiths (granite) and flood basalt provinces.
