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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.
Speaking broadly, mineral color points out the specific gravity of the mineral, as minerals that are lighter in color tend to be less dense. Darker minerals typically tend to contain more of relatively heavy elements, notably iron, magnesium, and calcium. [2] The temperature of crystallization affects what the color index of rocks tends to be. [10]
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 ...
Therefore, protogenetic inclusions provide information on the conditions that existed before diamond formation. This can explain isotopically different mineral inclusions found from the same generation of diamonds. [15] For syngenetic mineral inclusions, the crystallization of the trapped mineral and the diamond occur simultaneously. [1]
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 ...
They are usually dark in color, owing to the abundance of ferro-magnesian silicates, of high specific gravity and liable to decomposition. For these reasons they have been defined as a melanocrate series (rich in the dark minerals ); and they are often accompanied by a complementary leucocrate series (rich in the white minerals feldspar and ...
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Hornblende is a complex inosilicate series of minerals. [6] It is not a recognized mineral in its own right, but the name is used as a general or field term, to refer to a dark amphibole. Hornblende minerals are common in igneous and metamorphic rocks. The general formula is (Ca,Na) 2−3 (Mg,Fe,Al) 5 (Al,Si) 8 O 22 (OH,F) 2.