igneous
Granite / Gneiss Ballast Rock
Granite (Quartzo-feldspathic rock)
Hardness 6-7 on Mohs scale, earthy to dull luster, medium to coarse-grained texture. Color varies from gray, buff, greenish-gray to brownish iron-stained tones. Composed mainly of quartz, feldspar, and minor dark ferromagnesian minerals.
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Physical properties
Hardness 6-7 on Mohs scale, earthy to dull luster, medium to coarse-grained texture. Color varies from gray, buff, greenish-gray to brownish iron-stained tones. Composed mainly of quartz, feldspar, and minor dark ferromagnesian minerals.
Formation & geological history
Formed through the slow crystallization of magma deep beneath the Earth's surface. Mechanically crushed in modern quarries for heavy civil engineering applications such as railway track ballast.
Uses & applications
Widely crushed and used as railway ballast to support railroad ties, provide drainage, and hold track lines in place. Also used as aggregate in construction and road building.
Geological facts
Railway ballast rocks are selected specifically for their durability, angular shape (which prevents sliding under heavy trains), and resistance to weathering.
Field identification & locations
Identified by its angular, crushed shape, speckled mineral texture (quartz and feldspar visible), and frequent presence along railway tracks accompanied by iron rust staining from train wheels and rails.
