igneous

Wonderstone (Banded Rhyolite)

Rhyolite (Silicon Dioxide with Iron Oxide impurities)

Hardness: 6-7 on Mohs scale; Color: Red, tan, cream, and grey bands; Luster: Matte to earthy (waxy when polished); Crystal Structure: Aphanitic (fine-grained) to glassy; Cleavage: None (conchoidal fracture).

Hardness: 6-7 on Mohs scale
Color: Red, tan, cream, and grey bands
Luster: Matte to earthy (waxy when polished)

Identified March 14, 2026More igneous →

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Physical properties

Formation & geological history

Formed from volcanic eruptions where thick, silica-rich lava cools quickly. The distinct banding is caused by the flow of the lava and the oxidation of iron-bearing minerals (hematite or goethite) within the rock layers, often dated to the Tertiary period.

Uses & applications

Primarily used for ornamental purposes, lapidary work (cabochons, beads), decorative garden stones, and as a popular specimen for collectors due to its unique patterns.

Geological facts

Wonderstone is famous for its 'painterly' look, which can resemble desert landscapes. While it looks like sedimentary sandstone because of the bands, it is actually a hard volcanic rock that can take a high polish.

Field identification & locations

Identify in the field by its distinct colorful banding and its hardness (it will scratch glass, unlike similar-looking sandstone). Common locations include Nevada and Utah in the USA, and parts of South Africa.

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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)

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Sodalite - Na8(Al6Si6O24)Cl2

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Magnetite

Magnetite (Fe3O4)

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