igneous

Amygdaloidal Basalt

Hardness: 6-7 (groundmass); Color: Dark brown or black base with white/pink almond-shaped inclusions; Luster: Pearly to vitreous inclusions in a dull groundmass; Porphyritic/Vesicular texture.

Hardness: 6-7 (groundmass)
Luster: Pearly to vitreous inclusions in a dull groundmass

Identified May 9, 2026More igneous →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Hardness: 6-7 (groundmass); Color: Dark brown or black base with white/pink almond-shaped inclusions; Luster: Pearly to vitreous inclusions in a dull groundmass; Porphyritic/Vesicular texture.

Formation & geological history

Formed from volcanic lava flows where gas bubbles (vesicles) were later filled with secondary minerals like quartz, calcite, or zeolites through groundwater infiltration long after solidification.

Uses & applications

Used primarily as decorative garden stones, in lapidary work for cabochons, and as a geological teaching specimen.

Geological facts

The term 'amygdule' comes from the Greek word 'amygdala', meaning almond, referring to the shape of the mineral fillings. This specifically looks like 'Rice Rock' or 'Peanut Obsidian' texture common in certain volcanic regions.

Field identification & locations

Look for a dark, dense volcanic matrix containing distinct, oval-shaped light-colored mineral pockets. Commonly found in the Lake Superior region of the US and other ancient volcanic terrains.

Other igneous specimens

See all

Blue Apatite

Fluorapatite (Ca5(PO4)3F)

mineral

Dark Igneous Rock (Likely Basalt or Diabase)

Basalt (extrusive igneous rock) or Diabase (intrusive igneous rock - also known as Dolerite), largely composed of plagioclase feldspar, pyroxene (augite), and sometimes olivine and amphibole. Exact mineralogy would require thin section analysis.

Igneous