![amphibole ternary diagram amphibole ternary diagram](https://ars.els-cdn.com/content/image/1-s2.0-S1674987120301171-fx1.jpg)
Sodium-bearing amphiboles are represented by the glaucophane riebeckite series. Consequently, coexisting pairs of anthophyllite-tremolite and grunerite-ferroactinolite are found together in some rocks.
#Amphibole ternary diagram series#
Intermediate amphibole compositions do not exist between anthophyllite and the tremolite-actinolite series.įig.1: The amphibole quadrilateral composition diagram.Ĭompositional gaps also exist between the cummingtonite-grunerite series and other calcic amphiboles. The monoclinic cummingtonite-grunerite series exists from about Fe 2Mg 2Si 8O 22(OH) 2 to Fe 7Si 8O 22(OH) 2. The compositional range from Mg 7Si 8O 22(OH) 2 to about Fe 2Mg 5Si 8O 22(OH) 2is represented by the orthorhombic amphibole known as anthophyllite. Actinolite is the intermediate member of the tremolite-ferro-actinolite series. This diagram is commonly referred to as the amphibole quadrilateral.Ĭomplete substitution extends from tremolite to ferro-actinolite. Numerous common amphiboles can be represented within the Mg 7Si 8O 22(OH) 2 (anthophyllite), Fe 7Si 8O 22(OH) 2 (grunerite) and Ca 7Si 8O 22(OH) 2 (hypothetical pure calcium amphibole) compositional field ( Fig.1). The mineral nomenclature of the amphiboles is divided into four principal subdivisions based on B-group cation occupancy: (1) the iron-magnesium-manganese amphibole group, (2) the calcic amphibole group, (3) the sodic-calcic amphibole group, and (4) the sodic amphibole group. In 1997 Leake presented a precise nomenclature of 76 names that encompass the chemical variation within this group. The complexity of the amphibole formula has given rise to numerous mineral names within the amphibole group. Partial substitution of fluorine (F), chlorine, and oxygen for hydroxyl (OH) in the hydroxyl site is also common. Aluminum can partially substitute for silicon in the tetrahedral (T) site. There is limited substitution between ferric iron and aluminum and between titanium and other C-type cations. Nearly complete substitution may take place between sodium and calcium and among magnesium, ferrous iron, and manganese (Mn). Where where A = Na, K B = Na, Zn, Li, Ca, Mn, Fe 2+, Mg C = Mg, Fe 2+, Mn, Al, Fe 3+, Ti, Zn, Cr and T = Si, Al, Ti. The complex chemical composition of members of the amphibole group can be expressed by the general formula: The combination of prismatic form and two diamond-shaped directions of cleavage at about 56° and 124° is the diagnostic feature of most members of the amphibole group. Typically, amphiboles form as long prismatic crystals, radiating sprays, and asbestiform (fibrous) aggregates however, without the aid of chemical analysis, it is difficult to megascopically identify all but a few of the more distinctive end-member amphiboles. Because of the wide range of chemical substitutions permissible in the crystal structure, amphiboles can crystallize in igneous and metamorphic rocks with a wide range of bulk chemistries.
![amphibole ternary diagram amphibole ternary diagram](https://i.stack.imgur.com/58bg7.gif)
There are 5 major groups of amphiboles leading to 76 chemically defined end-member amphibole compositions according to the British mineralogist Bernard E. Amphiboles, from the Greek amphibolos, meaning ambiguous, was named by the famous French crystallographer and mineralogist René-Just Haüy in allusion to the great variety of composition and appearance shown by this mineral group.