igneous

Vesicular Basalt with Opal or Quartz

Vesicular Basalt (Amorphous SiO2.nH2O if Opal)

Hardness: 5.5-7 (Mohs scale), Color: tan to grayish exterior with small translucent inclusions, Luster: earthy matrix with vitreous/pearly inclusions, Crystal Structure: amorphous or microcrystalline, Cleavage: none, Specific Gravity: 2.1-3.0

Hardness: 5

Identified May 19, 2026More igneous →

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Physical properties

Formation & geological history

Formed from the rapid cooling of magnesium-rich and iron-rich lava. The holes (vesicles) were formed by gas bubbles. Later, silica-rich fluids filled these voids, creating the clear, slightly iridescent inclusions seen in the specimen.

Uses & applications

Primarily used for geological study, decorative gardening, and occasionally low-grade gemstone recovery if the inclusions are precious opal.

Geological facts

The rainbow flash visible in the clear section suggests a small 'play of color,' which is the defining characteristic of opal. This specific combination is often found in volcanic regions of Ethiopia or Australia.

Field identification & locations

Identify by looking for a porous, rocky matrix containing glassy or jelly-like 'pockets.' Commonly found in ancient volcanic fields. Collectors should look for flashes of color within the clear amygdules.

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