The term acidic rock refers to an igneous rock that consists mostly of light coloured minerals and has more than 66% free or combined silica. Research Acidic Rock
Andesite is a crystalline igneous rock, occurring mostly in lava flows, but sometimes in dykes and veins. It consists principally of plagioclasefeldspar, and is often porphyritic, showing large crystals of feldspar scattered through a fine-grained mass, usually of small feldspar crystals, but often containing much glassy material. Andesite forms most of the recent volcanic rock of the Andes, and is thus named after the Andes. Research Andesite
Basalt is an igneous rock, consisting of augite and triclinicfeldspar, with grains of magnetic or titanic iron, and also bottle-green particles of olivine frequently disseminated. It is usually of a greenish black colour, or of some dull brown shade, or black. It constitutes immense beds in some regions, and also occurs in veins or dikes cutting through other rocks. It has often a prismatic structure as at the Giant's Causeway, in Ireland, where the columns are as regular as if the work of art. It is a very tough and heavy rock, and is one of the best materials for macadamising roads. Research Basalt
Diabase is a dark, intrusive, basic igneous rock made up of plagioclasefeldspar crystals, surrounded by smaller grains of pyroxenes, such as augite and up to ten percent quartz. Diabase is formed from magna that has cooled just below the Earth's surface, and is sometimes found as intrusions in older rock. A common place to find diabase is in the neck of old volcanoes, where it has formed a plug. Research Diabase
In geology, a dike or dyke is a term applied to intrusions of igneous rock, such as basalt, greenstone, etc, which fill up veins and fissures in the stratified systems, and sometimes project on the surface like walls. Research Dike
Granodiorite is a plutonic igneous rock formed from cooling magma in deep zones of mountain belts. Granodiorite is a course-grained intermediate igneous rock comprised mainly of feldspar and quartz, and either pink or white in colour depending upon the proportions of feldspar and quartz. Research Granodiorite
Igneous intrusion refers to a body of igneous rock that has made its way into pre-existing rock (known as country rock). Igneous intrusions are emplaced as magma, which is less dense than solid rock and therefore tends to move upwards. It can then force its way through cracks in the rocks and can wedge them apart or, if it is hot enough, it can melt and replace them.
Igneous intrusions can be of a variety of shapes and sizes, ranging from huge batholiths to bodies only one or two meters across. The general term 'pluton' can be applied to any of these. Intrusions may cut across the bedding of the country rock. They are then termed 'discordant' or 'transgressive'; dykes and laccoliths are examples. Intrusions that follow the bedding of the country rock, such as sills, are termed 'concordant'. Research Igneous Intrusion
The Probert Encyclopaedia was designed, edited and programed by
Matt and Leela Probert
Abbreviations
Research Acidic Rock
