metamorphic
Greenstone Pebble
Metabasalt (often containing chlorite, actinolite, or epidote)
Hardness: 5-7 (Mohs scale), Color: Dull to dark green with possible white calcite/quartz veins, Luster: Dull to waxy, Crystal structure: Massive/fine-grained, Specific gravity: 2.8-3.0
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Physical properties
Hardness: 5-7 (Mohs scale), Color: Dull to dark green with possible white calcite/quartz veins, Luster: Dull to waxy, Crystal structure: Massive/fine-grained, Specific gravity: 2.8-3.0
Formation & geological history
Formed through low-grade regional metamorphism of mafic igneous rocks (like basalt or gabbro). Often found in ancient volcanic belts dating from the Archean to Proterozoic eons.
Uses & applications
Commonly used as crushed stone for construction, architectural veneer, or as decorative river rock. Historically used for making stone tools (celts and axes) due to its toughness.
Geological facts
The 'green' color comes from minerals like chlorite and epidote that form under specific temperature and pressure conditions known as the 'greenschist facies.'
Field identification & locations
Identify by its distinctive dull green hue and find it in glacial till or riverbeds near volcanic belts. Tips: Check if it scratches steel to differentiate from softer stones.
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