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Minette (a type of lamprophyre), from Jáchymov in the Czech Republic. Lamprophyres (from Ancient Greek λαμπρός (lamprós) 'bright' and φύρω (phúrō) 'to mix') are uncommon, small-volume ultrapotassic igneous rocks primarily occurring as dikes, lopoliths, laccoliths, stocks, and small intrusions.
dike. Also spelled dyke. A type of sheet intrusion referring to any geologic body that cuts discordantly across. A form of minor intrusion injected into the crust during its subjection to tension, the dyke being thin with parallel sides, and maintaining a constant direction in some cases for long distances.
The sapphire bearing Yogo dike is a dark gray to green intrusive rock known as a lamprophyre. The lamprophyre is an unusual igneous rock that contains a low content of silica . The rock has a porphyritic texture with large crystals of orthopyroxene and phlogopite set in a fine grained matrix .
A dike of lamprophyre near the Shiprock volcanic plug, New Mexico, that has resisted the erosion that removed some of the softer rock into which the dike was originally intruded. A magmatic dike is a sheet of igneous rock that cuts across older rock beds.
Sample of lamproite [1]. Lamproite is an ultrapotassic mantle-derived volcanic or subvolcanic rock.It has low CaO, Al 2 O 3, Na 2 O, high K 2 O/Al 2 O 3, a relatively high MgO content and extreme enrichment in incompatible elements.
Lamprophyre from the Piégut-Pluviers Granodiorite. Lamprophyre dikes are fairly common in the metamorphic country rocks of the granodiorite, but extremely rare in the massif itself. Unweathered lamprophyres have a dark green to green colour; they are very dense fine-grained rocks that weather in creamy colours.
Phyllite Banded gneiss with a dike of granite orthogneiss Marble Quartzite Manhattan Schist, from Southeastern New York Slate. Anthracite – Hard, compact variety of coal; Amphibolite – Metamorphic rock type; Blueschist – Type of metavolcanic rock; Cataclasite – Rock found at geological faults – A rock formed by faulting
Dacite usually forms as an intrusive rock such as a dike or sill. Examples of this type of dacite outcrop are found in northwestern Montana and northeastern Bulgaria. Nevertheless, because of the moderately high silica content, dacitic magma is quite viscous [9] and therefore prone to explosive eruption.