igneous
Weathered basalt (likely vesicular basalt)
Basalt; chiefly plagioclase feldspar, clinopyroxene, and olivine, with possible iron-oxide alteration
AI-generated identification · may be incorrectDark gray-brown, fine-grained and massive, with uneven fracture and possible small vesicles; dull to subvitreous luster. Hardness about 5–6 Mohs; cleavage is not apparent; specific gravity roughly 2.8–3.1.
Identified More igneous →
Explore Weathered basalt (likely vesicular basalt) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Dark gray-brown, fine-grained and massive, with uneven fracture and possible small vesicles; dull to subvitreous luster. Hardness about 5–6 Mohs; cleavage is not apparent; specific gravity roughly 2.8–3.1.
Formation & geological history
An extrusive mafic igneous rock formed when basaltic lava cooled rapidly at or near Earth’s surface, commonly during volcanic eruptions. Its brown-yellow surface likely reflects weathering and oxidation; age cannot be determined from the photograph.
Uses & applications
Used as crushed aggregate, road base, riprap, and occasionally building stone; ordinary specimens have little jewelry value.
Geological facts
Basalt is the most abundant volcanic rock on Earth and forms much of the oceanic crust. Yellow-brown coloration commonly results from limonite or other iron-oxide minerals filling weathered areas or vesicles.
Field identification & locations
In the field, look for a dense dark fine-grained interior, high weight, and lack of visible large crystals; a streak, fresh break, and hand lens would improve identification. Common worldwide, especially in volcanic regions and oceanic terrains.
