lamprophyre

There is also a minor intrusion of lamprophyre in this area.

It is an essential phenocryst in some varieties of lamprophyre.

Each variety of lamprophyre may and often does contain all four minerals but is named according to the two which predominate.

There are many small intrusions of lamprophyre and diorite.

The lamprophyre is an unusual igneous rock that contains a low content of silica.

The climbing cliffs feature subtypes of that rock like ferrodiorite and lamprophyre.

On a purely chemical basis, an extrusive lamprophyre (sp.

Modern nomenclature has been derived from an attempt to constrain some genetic parameters of lamprophyre genesis.

Lamprophyre dykes of Late Permian age are found throughout Orkney.

This has, by and large, dispensed with the previous provincial names of lamprophyre species, in favor of a mineralogical name.

Dykes of lamprophyre and more rarely dolerite are exposed in many parts of Orkney.

Several varieties of carbonatite are present in the area as well as lamprophyre, ijolite and other highly alkalic rocks.

Ultrapotassic, ultramafic igneous rocks such as lamprophyre, lamproite and kimberlite are known to have reached the surface of the Earth.

Dolerite (or diabase) and lamprophyre dykes intruded.

This suggests the sapphire crystals may have originated in an earlier rock, such as a corundum-bearing gneiss, later assimilated by the lamprophyre magma at depth.

Radiometric dates of 1883-1870 Ma are reported for mafic, ultramafic, carbonatite and lamprophyre intrusions within the Trough.

Typically, primitive melts of this composition form lamprophyre, lamproite, kimberlite and sometimes nepheline-bearing mafic rocks such as alkali basalts and essexite gabbros or even carbonatite.

Phlogopite mica is a commonly known phenocryst and groundmass phase within ultrapotassic igneous rocks such as lamprophyre, kimberlite, lamproite, and other deeply sourced ultramafic or high-magnesian melts.

This system was based on a somewhat provincial, rustic system of naming after French villages nearby were found the first described examples of various species of Lamprophyre (Vosges being the prime example).

The Yogo sapphires themselves are rimmed with a reaction layer of spinel and are etched, indicating that the sapphires were not in chemical equilibrium with their host, the lamprophyre magma.