|
(AMPHIBOLES) (Na,K)0-1Ca2(Mg,Fe,Al)5[Si6-7Al2-1O22](OH,F)2
Crystal system: Monoclinic
Refractive index: 1.615-1.730
Birefringence: 0.014-0.026
Cleavage: two good 56o
Twinning: simple, lamellar, common
Colour in PPL: pale green, green, yellow-brown, brown
Pleochroism: moderate to strong
Relief: moderate
Distinction: hornblende distinguished from actinolite by extinction angle between 10o and 15o of later (13o - 35o
in hornblende)
Occurrence: wide range of igneous and metamorphic rocks, with subsequent wide range in chemistry
|
Hornblende - Plain polarised light - Faza petrofabric, Yemen - Field of view 1mm
|
