Twin systematic of the monoclinic potassium feldspars as a result of their "Faden" growth in the alpine-type veins
Žorž, Mirjan; Follner, Heinz; Mirtic, Breda; Golic, Ljubo
published: Mar 24, 1998
ArtNo. ESP154017301001, Price: 29.00 €
Monoclinic potassium feldspars are frequently encountered in the alpinetype veins in the form of adularia and hyalophane crystals. They can form simple Karlsbad, Manebach, Baveno and Manebach-Baveno twins. Additionally, more complex twins deriving from their simple basic forms can be found in these veins. The development of their complex morphological structures can be ascribed to the elongation of the particular crystal, twin or combination twin during the vein widening process. Elongation of the Karlsbad twin results in 6 types of single and 9 types of double Karlsbad twins. Elongation of the Manebach or Baveno twin results in one single and one double twin type. The elongations of two types of Manebach-Baveno combination twins (fourlings) denoted as (010)- and (001)-fourling produce two corresponding single fourlings and two types of double fourlings, i. e. (010)- (010)- and (001)- (010)-double fourling. Secondary Manebach twinning caused by the breaking of the primary single or twin crystal has a crucial role in the formation and development of most elongated twin types.
Faden crystal growth • monoclinic potassium feldspars • Karlsbad twin • Manebach twin • Baveno twin (pseudo fourling)(010)-and(001)-Manebach-Baveno combination twins (fourlings) • double Karlsbad twin • inverted Manebach twin • double Baveno twins • double (010)-(010)-Manebach-Baveno and (001)-(010)-Manebach-Baveno combination twin (double fourling) • elongation of single crystal • twin and combination twin • secondary