Basalt

Basalt is a commonly occurring igneous rock which exhibits a fine crystalline texture and dark (often black or dark brown) colouration. Due to its chemistry, it is fairly dense and almost often forms as an extrusive rock, which is when molten magma erupts (extrudes) onto the earths surface. These particular specimens are from Northern Ireland and are a part of the Antrim lava group. The basalt (which also includes the famous Giants Causeway) are dated to approximately 60 million years old to the Tertiary period. Their chemistry suggests that the rock is olivine basalt and comprises of plagioclase feldspar, olivine, augite, though other minor mineral may be present. Basalt, being so common, is a suitable beginner collectors sample and an important rock for educational use due to how it forms as well as an important component in palaeomagnetism which allows geologists to observe and study the movement of the earths magnetic poles through out geological time. The specimens we supply of this rock are available in 3 sizes and come supplied in a white card tray with a small label.