Group I kimberlites exhibit a distinctive inequigranular texture caused by macrocrystic ( ) to megacrystic ( ) phenocrysts of olivine, pyrope, chromian diopside, magnesian ilmenite and phlogopite, in a fine to medium grained groundmass.
32.
The distinctive characteristic of olivine lamproites is phlogopite macrocrysts and microphenocrysts, together with groundmass micas that vary in composition from phlogopite to " tetraferriphlogopite " ( anomalously Al-poor phlogopite requiring Fe to enter the tetrahedral site ).
33.
The distinctive characteristic of olivine lamproites is phlogopite macrocrysts and microphenocrysts, together with groundmass micas that vary in composition from phlogopite to " tetraferriphlogopite " ( anomalously Al-poor phlogopite requiring Fe to enter the tetrahedral site ).
34.
The distinctive characteristic of olivine lamproites is phlogopite macrocrysts and microphenocrysts, together with groundmass micas that vary in composition from phlogopite to " tetraferriphlogopite " ( anomalously Al-poor phlogopite requiring Fe to enter the tetrahedral site ).
35.
Hydrated minerals ( e . g ., phlogopite, lawsonite, amphibole ) within the oceanic lithosphere become unstable at certain depths due to increased temperature and pressure, causing the crystal structure of the hydrated minerals break down and release water.
36.
The most famous of the rocks of Aln�n is the " alnoite ", named from the Island, which is a lamprophyre chiefly composed of biotite or phlogopite and melilite as essential minerals, commonly with olivine, calcite and clinopyroxene.
37.
The occurrence of phlogopite mica within igneous rocks is difficult to constrain precisely because the primary control is rock composition as expected, but phlogopite is also controlled by conditions of crystallisation such as temperature, pressure, and vapor content of the igneous rock.
38.
The occurrence of phlogopite mica within igneous rocks is difficult to constrain precisely because the primary control is rock composition as expected, but phlogopite is also controlled by conditions of crystallisation such as temperature, pressure, and vapor content of the igneous rock.
39.
Group-I kimberlites are of CO 2-rich ultramafic potassic igneous rocks dominated by primary forsteritic olivine and carbonate minerals, with a trace mineral assemblage of magnesian ilmenite, chromium pyrope, almandine-pyrope, chromium diopside ( in some cases subcalcic ), phlogopite, enstatite and of Ti-poor chromite.
40.
A second great group of hornfels are the recrystallize as marbles, but where there has been originally an admixture of sand or clay lime-bearing silicates are formed, such as diopside, epidote, garnet, sphene, vesuvianite and scapolite; with these phlogopite, various feldspars, pyrites, quartz and actinolite often occur.
