Describe how the optical properties of phlogopite different than biotite. Phlogopite is the magnesium endmember of the biotite solid solution series, with the chemical formula KMg 3 AlSi 3 O 10 (F,OH) 2. It is also known as magnesium mica.Phlogopite is the magnesium endmember of the biotite solid solution series, with the chemical formula KMg 3 (AlSi 3 O 10)(OH,F) 2. Nearly pure phlogopite is found in hydrous ultrabasic rocks like kimberlite, and is also found in metamorphosed dolomites. Iron substitutes for magnesium in variable amounts leading to the more common biotite with higher iron content. Phlogopite is rarely considered a valuable mineral specimen and is ⦠It may be pleochroic, but not as much as the Fe-rich biotites. Optical properties of the phlogopite are summarized in Table 1. Phlogopite occurs typically as a metamorphic product (e.g., in crystalline metamorphosed limestones) and also in ultramafic igneous rocks. Previous question Next question Get more help from Chegg. Optical Properties: Biaxial 1- 2, a = 1.56, b = 1.60, g = 1.60, d = 0.04, 2V = 0° to 20°. Question: Describe How The Optical Properties Of Phlogopite Different Than Biotite. The darker color and density increase with an increase in the iron content. Expert Answer . Optical Properties : Phlogopite is similar to other micas in thin section. K(Mg,Fe) 3 AlSi 3 O 10 (OH) 2 Phlogopite refers to micas at the magnesian end (Mg/(Mg+Fe) > 0.67) of the biotite-phlogopite solid solution series.Phlogopite has many of the optical characteristics of biotite, with the most important difference being that phlogopites are less strongly coloured (i.e., the pleochroic colours are not as intense). Cliemical Composition. Phlogopite is iron poor and Biotite is iron rich. For physical and optical identification, it shares most of the characteristic properties of biotite. This problem has been solved! Phlogopite. Chemical Formula: KMg 3 (AlSi 3 O 10)(OH,F) 2 Name Origin: From the Greek flogopos â âresembling fire.âPhlogopite is a yellow, greenish, or reddish-brown member of the mica family of phyllosilicates. Biotite, with more Fe-rich compositions is common in dacitic, rhyolitic, and trachytic volcanic rocks, granitic plutonic rocks, and a wide variety of metamorphic rocks. For physical and optical identification, it shares most of the characteristic properties of biotite. Chocolate consists of cocoa butter, cocoa particles, sugar, and additives, which together determine its taste and optical properties. Phlogopite, like other Micas, has a layered structure which produces its perfect cleavage. Phlogopite is the magnesium endmember of the biotite solid solution series, with the chemical formula KMg 3 AlSi 3 O 10 (F,OH) 2.Iron substitutes for magnesium in variable amounts leading to the more common biotite with higher iron content. See the answer. For physical and optical identification, it shares most of the characteristic properties of biotite. The optical properties of chocolate play a vital role in consumer perception, representing type and quality in the blink of an eye. It has a smaller 2V than muscovite and is often col-ored light brown. Main members â phlogopite (KMg 3 (AlSi 3 O 10) (OH) 2) as Mg end-member, annite (K Fe 3 2 + (AlSi 3 O 10) (OH) 2) as Fe end-member.