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In mineralogy, an inclusion is any material trapped inside a mineral during its formation. In gemology , it is an object enclosed within a gemstone or reaching its surface from the interior. [ 1 ] According to James Hutton 's law of inclusions, fragments included in a host rock are older than the host rock itself.
The aluminium-bearing minerals of these fragments provide clues to the depth of origin. Calcic plagioclase is stable to a depth of 25 km (16 mi). Between 25 km (16 mi) and about 60 km (37 mi), spinel is the stable aluminium phase. At depths greater than about 60 km, dense garnet becomes the aluminium-bearing
The timing of mineral crystallization can be used to categorize diamond inclusions into three types: protogenetic, syngenetic, and epigenetic inclusions. [14] Minerals in the protogenetic inclusions were crystallized earlier than the diamond formation. The host diamond encapsulated pre-existing minerals during its crystallization.
Hydrothermal ore minerals, which typically form from high temperature aqueous solutions, trap tiny bubbles of liquids or gases when cooling and forming solid rock. The trapped fluid in an inclusion preserves a record of the composition, temperature and pressure of the mineralizing environment. [1] An inclusion often contains two or more phases ...
Nepheline is a feldspathoid, a solid-solution mineral, that does not coexist with quartz; rather, nepheline would react with quartz to produce alkali feldspar. They are distinguished from syenites not only by the presence of nepheline but also by the occurrence of many other minerals rich in alkalis and in rare earths and other incompatible ...
The inclusion of sodium, which has a charge of +1, into the pyroxene implies the need for a mechanism to make up the "missing" positive charge. In jadeite and aegirine this is added by the inclusion of a +3 cation (aluminium and iron(III) respectively) on the Y site.
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Each mineral, depending on the orientation, may not exhibit the maximum birefringence. It is important to sample a number of similar minerals in order to get the best value of birefringence. Uniaxial minerals can look isotropic (always extinct) if the mineral is cut perpendicular to the optic axis (this situation can be revealed with the ...