igneous
Railway Ballast (Crushed Traprock / Basalt with Iron Oxide Staining)
Mafic Volcanic Rock (Basalt / Diabase with Fe2O3.nH2O limonite coatings)
Hardness: 6-6.5 on Mohs scale. Color: Dark grey to greenish-grey body with bright orange-brown iron oxide (rust) surface weathering. Luster: Dull to earthy. Texture: Fine-grained (aphanitic to microcrystalline). Cleavage: None, fractures conchoidally to irregularly.
- Hardness
- 6-6
- Luster
- Dull to earthy
Identified More igneous →
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Physical properties
Hardness: 6-6.5 on Mohs scale. Color: Dark grey to greenish-grey body with bright orange-brown iron oxide (rust) surface weathering. Luster: Dull to earthy. Texture: Fine-grained (aphanitic to microcrystalline). Cleavage: None, fractures conchoidally to irregularly.
Formation & geological history
Formed from rapid cooling of mafic lava or near-surface magma intrusions rich in magnesium and iron. The surface iron staining developed from weathering and proximity to rusting steel railway tracks.
Uses & applications
Extensively quarried and crushed for use as railroad track ballast, road construction aggregate, concrete aggregate, and riprap.
Geological facts
Railroad ballast stones are chosen specifically for their angular shape, high density, and durability, which prevents track movement, provides drainage, and supports heavy train loads.
Field identification & locations
Identified by its fine-grained dark grey matrix, sharp angular fractures, and rusty iron-oxide surface coatings when found near rail lines. Abundant along railway beds worldwide.
