What is the chemical formula for feldspar?
|Feldspar crystal (18×21×8.5 cm) from Jequitinhonha valley, Minas Gerais, southeastern Brazil|
|Formula (repeating unit)||KAlSi 3O 8 – NaAlSi 3O 8 – CaAl 2Si 2O 8|
Which feldspar has exsolution lamellae?
The exsolution lamellae of Na- and K-rich feldspar are created in the bulk composition of the K-feldspar. A Na-rich host with K-rich lamellae is an antiperthite.
What is the chemical formula for potassium feldspar?
classification. Microcline and orthoclase are potassium feldspars (KAlSi3O8), usually designated Or in discussions involving their end-member composition. Albite (NaAlSi3O8—usually designated Ab) and anorthite (CaAl2Si2O8—An) are end-members of the plagioclase series.
What is a exsolution lamellae in geology?
[¦ek·sə′lü·shən lə′mel·ē] (geology) Layers of sedimentary rock that solidify from solution by either precipitation or secretion.
What chemicals are in feldspar?
All the rock-forming feldspars are aluminosilicate minerals with the general formula AT4O8 in which A = potassium, sodium, or calcium (Ca); and T = silicon (Si) and aluminum (Al), with a Si:Al ratio ranging from 3:1 to 1:1.
What is exsolution in geology?
exsolution, in mineralogy, process through which an initially homogeneous solid solution separates into at least two different crystalline minerals without the addition or removal of any materials.
Does plagioclase have exsolution?
Plagioclase feldspars exhibit exsolution microtextures in three compositional ranges, the Peristerite, Bøggild and Huttenlocher ‘miscibility gaps’ shown in orange on Fig.
What is Zeolite formula?
Zeolites are the aluminosilicate members of the family of microporous solids known as “molecular sieves”, and mainly consist of silicon, aluminum, oxygen, and have the general formula MxAlxSi1−xO2·yH2O where M is either a metal ion or H+.
What is the chemical composition of plagioclase feldspar?
|Physical Properties of Plagioclase|
|Diagnostic Properties||Perfect cleavage, with cleavage faces intersecting at right angles and striations often present on cleavage faces. Well-defined crystals are extremely rare.|
|Chemical Composition||NaAlSi3O8 – CaAl2Si2O8|
What is exsolution solid solution?
exsolution, in mineralogy, process through which an initially homogeneous solid solution separates into at least two different crystalline minerals without the addition or removal of any materials. In most cases, it occurs upon cooling below the temperature of mutual solubility or stability of the solution.
Which mineral has the exsolution lamellae structure?
Potassium feldspar (also orthoclase feldspar or K-spar) exhibits bands of different color on cleavage surfaces. These bands, or exsolution lamellae, are planar zones of slightly different composition.
What is the chemical name of feldspar?
The form of alkali metal or alkaline earth metal found in the molecule determines the chemical name of feldspar. These minerals are a class of rock-forming tectosilicate minerals that account for around 41% of the continental crust’s weight. Tectosilicates, or silicate minerals, are a type of natural mineral.
Is feldspar a tectosilicate?
Feldspars are a group of rock-forming aluminium tectosilicate minerals, containing sodium, calcium, potassium or barium. The most common members of the feldspar group are the plagioclase (sodium-calcium) feldspars and the alkali (potassium-sodium) feldspars.
What are exsolution lamellae and how do they occur?
The exsolution lamellae are crystallographically controlled by the host minerals. They occur as one or more groups of oriented rods/needles strictly aligned along the structural defects of the host minerals. Exsolution texture induced by cooling: Clinopyroxene (Cpx) exsolution in orthopyroxene (Opx) or vice versa.
What is barium feldspar?
It is a mineral associated with hydrothermal alteration of the primary feldspar minerals. Barium feldspars form as the result of the substitution of barium for potassium in the mineral structure. Barium feldspars are sometimes classified as a separate group of feldspars, and sometimes they are classified as a sub-group of alkali feldspars.