Ballast Basalt,Traprock,Granite Gravel,Tumbled Basalt for Railroad,Harbours,marinas - bslt01

Traprock is not a geological term. It is a term used in the quarrying (mining) and rock commodities industries to refer to any number of dark-colored igneous rocks that are crushed and used, primarily, for road construction. The most common rock type in the traprock category are gabbro and basalt. Dark-colored igneous rocks have high iron and magnesium contents and relatively lower silica content (compared to continental crustal rocks, like granite, that have high silica contents and very low iron and magnesium contents). This dark magma originates in the Earths mantle. Dark igneous rock that is intruded into the crust cools more slowly and becomes coarse-grained. Geologists call this rock gabbro. When it is extruded onto the crusts surface, it cools quickly and becomes fine-grained. Geologists refer to this as basalt. Diabase is another fine-grained igneous rock that is considered traprock. Diabase is composed mostly of the minerals feldspar and pyroxene.
Traprock is commonly found intruded between layers of pre-existing rock. Liquid rock that is intruded into the crust is referred to as plutonic rock and the mass of hardened magma is called a pluton. In some geologic settings, the magma does not intrude into the surrounding country rock, but pours out onto the surface in thick flows. Geologists call such flows sills.

^USES

Traprock is used primarily as crushed rock for road construction. It is also crushed and mixed into concrete . Crushed traprock is also used as railroad ballast. Railroad ballast is crushed rock poured between railroad ties to complete the bed on which trains run.

Some traprock is cut and polished for use as dimension stone in construction. It is used as veneers on buildings, and is cut for use as tiles and other decorative construction purposes. Traprock can be polished to a very high polish. Because of its dark green to black color and ability to be polished, it has found some popularity as a material for headstones.