AXINITE
Axinite is a calcium manganese iron magnesium
hydroxy-alumino-borosilicate mineral, Ca2(Mn,Fe,Mg)Al2BSi4O15(OH).
The term "axinite" is used to refer to mineral samples having this
general formula and is also used to refer to a group of minerals.
Fe-rich axinite (ferro-axinite, or axinite-(Fe)) appears to be the most common
mineral in the axinite group. Manganese-rich, magnesium-rich, and
iron-manganese-rich versions have separate names (manganaxinite or axinite-(Mn)
& magnesio-axinite or axinite-(Mg) & tinzenite, respectively).
Axinite crystallizes in the triclinic system,
resulting in crystals with no planes of symmetry. Axinite has a
nonmetallic, glassy luster, varies widely in color (brown, purplish brown,
reddish brown, grayish, bluish, black, yellowish, yellowish-orange, clear,
etc.), has a white streak, a hardness of about 6 to 7, and has one good
cleavage plane. It's also relatively brittle, having uneven to conchoidal
fracture.
Axinite crystals are transparent to translucent and
have flattened, wedge-like shapes. Some axinite occurs as thinly layered
material or in massive to granular forms. Some of the axinite crystal
faces have striations.
Axinite has been principally reported in some regional
metamorphic rocks, some contact metamorphic rocks, and some pegmatitic
granites.
Axinite
from the Obira Mine, Oita Prefecture, Japan.
Specimen owned by John Rakovan.
Photo gallery of
ferro-axinite (= Fe-rich axinite)
Photo gallery of
manganaxinite (= Mn-rich axinite)
Photo gallery of
mangesio-axinite (= Mg-rich axinite)
Photo gallery of tinzenite
(= FeMn-rich axinite)