igneous

Amygdaloidal Basalt

Amygdaloidal Basalt containing Zeolite and Calcite inclusions

Hardness: 5-7 (matrix) / 3-5 (inclusions). Color: Dark gray to black matrix with white or light green spots. Luster: Dull/earthy matrix, vitreous/pearly inclusions. Texture: Vesicular or amygdaloidal.

Hardness: 5-7 (matrix) / 3-5 (inclusions)
Color: Dark gray to black matrix with white or light green spots
Luster: Dull/earthy matrix, vitreous/pearly inclusions

Identified April 11, 2026More igneous →

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Physical properties

Formation & geological history

Formed from cooled volcanic lava (Basalt). The 'amygdules' (the white spots) formed when gas bubbles (vesicles) were later filled with secondary minerals like calcites, zeolites, or quartz through hydrothermal fluid activity.

Uses & applications

Used primarily in road construction and as aggregate. Specific amygdaloidal specimens are valued by geological collectors for their mineral diversity.

Geological facts

The word 'amygdule' comes from the Greek word 'amygdala', meaning almond, referring to the almond-shaped mineral fillings within the rock.

Field identification & locations

Identified by the dark, fine-grained volcanic matrix punctuated by rounded, lighter-colored mineral 'pockets'. Commonly found in volcanic rift zones like the Lake Superior region or the Deccan Traps.

Other igneous specimens

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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

Magnetite

Iron(II,III) oxide (Fe3O4)

mineral

Sodalite

Sodalite - Na8(Al6Si6O24)Cl2

mineral

Blue Apatite

Apatite (Group), Ca5(PO4)3(F,Cl,OH)

mineral

Magnetite

Magnetite (Fe3O4)

mineral