igneous
Amygdaloidal Basalt with Quartz Veining
Basalt (Extrusive Igneous Rock) with Quartz (SiO2) veining
Hardness: 6-7 (basalt/quartz), Color: Dark grey to charcoal with white quartz band, Luster: Dull to earthy (matrix) / vitreous (vein), Structure: Fine-grained/aphanitic with amygdule-like pockets and a hydrothermal vein.
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Physical properties
Hardness: 6-7 (basalt/quartz), Color: Dark grey to charcoal with white quartz band, Luster: Dull to earthy (matrix) / vitreous (vein), Structure: Fine-grained/aphanitic with amygdule-like pockets and a hydrothermal vein.
Formation & geological history
Formed from rapidly cooling lava flows. The white stripe is a secondary mineral deposit (hydrothermal quartz) that filled a crack in the rock after it consolidated. This specimen has been rounded by fluvial or beach erosion.
Uses & applications
Landscaping, road aggregate (in bulk form), or as decorative garden stones and pocket rocks for collectors.
Geological facts
The white line is known as a 'wishing stone' in some cultures—a rock with a single continuous white band. It represents hydrothermal activity where mineral-rich water cooled in a fissure.
Field identification & locations
Found commonly on beaches and in riverbeds. Look for dark, heavy volcanic rocks with starkly contrasting mineral lines. It is an excellent example of basic igneous petrology and secondary mineralization.
