macle de l'albite

CONT: La macle de l'albite, dite encore polysynthétique, donne en lumière polarisée une alternance de bandes claires et foncées.
OBS: macle : Assemblage régulier de deux ou plusieurs individus cristallins de même nature. [...] Ces macles sont très fréquentes dans les minéraux (ex. gypse, quartz, pyrite, aragonite, rutile, albite, péricline, fluorite, or, etc.).

CONT: If the regions are related such that they share a common c direction, the twin plane being the old mirror plane of the monoclinic structure, the twin is termed an albite twin.
CONT: Albite twin. The plagioclase feldspars, particularly albite ..., are frequently twinned on the albite law ... where the twin-plane and composition plane is (010). This twinning is often repeated to give a series of five lamellae, seen in the hand specimens as striations...; such twinning is usually called ""polysynthetic"" or ""lamellar"" twinning.