خصوصیات بلور شناسی هورنبلند

HORNBLENDE

General Formula: (Na,K)0-1Ca2(Mg,Fe^2+,Fe^3+,Al)5(Si,Al)8O22(OH)2	Sample: AUPI-37	System: Monoclinic
Euhedral Hornblende Phenocrysts Numerous hornblende phenocrysts, exhibiting a range of pleochroic colours, euhedral shapes and two cleavages which intersect at 56-124°:. Field of View = 2.7 mm, plane light	Euhedral Hornblende Phenocrysts Note that the interference colour exhibited by the individual hornblende grains is masked to some degree by the dark colour of the grain. Field of view = 2.7 mm, crossed polars	Block diagram showing the relationship between the crystallographic axes and the indicatrix axes.

Optical Properties

Colour Pleochroism	distinctly coloured, shades of green, yellow-green, blue-green and brown X = light yellow, light yellow green, light blue green Y = green, yellow green, gray-green, brown Z = dark green, dark blue-green, dark gray-green, dark brown	Form	found as slender prismatic to bladed crystals, with a 4 or 6 sided cross section which exhibit amphibole cleavage at 56 and 124°, also as anhedral irregular grains
Relief RI	moderate to high nalpha = 1.60-1.70 nbeta = 1.61-1.71 ngamma = 1.62-1.73	Cleavage	amphibole cleavages on {110} intersect at 56-124° fragment shape is controlled by cleavage
Birefringence Interference Colours	0.014-0.034 usually upper first or lower second order, but may be masked by mineral colour	Twinning	simple and lamellar twins on {100} are not uncommon
Interference Figure Optic Sign 2VX	biaxial positive or negative 35 - 130°	Optic Orientation	X^a = +3 to -19°, Y = b, Z^c = +12 to +34°, optic plane = (010) basal sections exhibit symmetrical extinction with the slow ray parallel to the long diagonal between the cleavages, longitudinal sections are length slow
Composition	exhibits a wide range of compositions	Alteration	may be altered to biotite, chlorite or other Fe-Mg silicates
Occurrence	common mineral found in a variety of geological environments, i.e. in igneous, metamorphic and sedimentary rocks	Distinguishing Features	cleavage and grain shape, inclined extinction, pleochroism

خصوصیات بلورشناسی مسکوویت

MUSCOVITE

General Formula: KAl2(Al,Si3O10)(OH)2	Sample: PT-51	System: Monoclinic
Muscovite Flakes Elongated, colourless flakes of muscovite, in a pelite from the Grenville Supergroup, Central Metasedimentary Belt of the Grenville Province. Field of view = 2.7 mm, plane light	Muscovite Flakes The flakes of muscovite display the characteristic second order blue interference colour. Note that the muscovite flakes define the fabric in the sample, with all exhibiting an EW orientation. Field of view = 2.7 mm, crossed polars	Block diagram showing the relationship between the crystallographic axes and the indicatrix axes.

Optical Properties

Colour Pleochroism	colourless non pleochroic	Form	found as micaceous flakes or tablets with irregular outlines
Relief RI	moderate positive nalpha = 1.552-1.580 nbeta = 1.582-1.620 ngamma = 1.587-1.623	Cleavage	perfect on {001}
Birefringence Interference Colours	0.036-0.049 vivid second order blues and greens	Twinning	rare
Interference Figure Optic Sign 2V	biaxial negative 30-47°	Optic Orientation	parallel extinction, cleavage traces are length slow
Composition	highly variable	Alteration	not generally altered
Occurrence	common in a wide variety of metamorphic rocks, felsic igneous rocks and as detrital grains in sedimentary rocks	Distinguishing Features	colourless, parallel extinction, "birds-eye" extinction

خصوصیات بلور شناسی بیوتیت

BIOTITE

General Formula: K2(Mg,Fe)3AlSi3O10(OH,O,F2)2	Sample: PT-104	System: Monoclinc
Biotite Porphyrobalsts Randomly oriented biotite porphyroblasts, exhibiting a range of pleochroic colours, in a pelite collected from the Meguma Group, Nova Scotia. Note the higher relief garnet grain in the lower left corner Field of view = 4 mm, plane light	Biotite Porphyroblasts The biotite porphyroblasts display a range of interference colours, and "bird's eye" extinction where the cleavge traces are parallel or nearly parallel to the polars (NS and EW). Field of view = 4 mm, crossed polars	Block diagram showing the relationship between the crystallographic axes and the indicatrix axes.

Optical Properties

Colour Pleochroism	typically brown, browhish green or reddish brown distinctly pleochroic	Form	tabular crystals parallel to {001} with a rough hexagonal shape, also as micaceous or tabular grains or grains with irregular outlines
Relief RI	moderate to moderately high positive nalpha = 1.522-1.625 nbeta = 1.548-1.672 ngamma = 1.549-1.696	Cleavage	perfect cleavage on {001}
Birefringence Interference Colours	0.03-0.07 up to third or fourth order, a strong mineral colour may mask the interference colour	Twinning	rarely visible
Interference Figure Optic Sign 2V	biaxial negative 0-25°	Optic Orientation	extinction is parallel or nearly parallel, with a maximum extinction angle of a few degrees. Cleavage traces are length slow.
Composition	variable composition	Alteration	alters to chlorite, clay minerals, and/or sericite, iron-titanium oxides, epidote, calcite, and sulphides
Occurrence	common in a wide range of igneous and metamorphic rocks and may be an important detrital mineral in sediments	Distinguishing Features	colour, pleochroism, "birds-eye" extinction, nearly parallel extinction

خصوصیات بلورشناسی الیوین

OLIVINE

General Formula: (Fe,Mg)2SiO4	Sample: PT-96	System: Orthorhombic
TITLE DESCRIPTION SCALE	TITLE DESCRIPTION SCALE	Block diagram showing the relationship between the crystallographic axes and the indicatrix axes.

Optical Properties

Colour Pleochroism	usually colourless, darker colours correspond to higher iron content non pleochroic	Form	generally subequant anhedral grains or aggregates in intrusive and metamorphic rocks. Equidimensional or elongated euhedral grains in volcanics
Relief RI	high positive nalpha = 1.636-1.827 nbeta = 1.651-1.869 ngamma = 1.669-1.879	Cleavage	not observed
Birefringence Interference Colours	0.033-0.052 up to third order	Twinning	not common
Interference Figure Optic Sign 2V	biaxial positive or negative 46-98°	Optic Orientation	elongate grains have parallel extinction and may be either length fast or slow
Composition	minor substitution of Mn, Zn, Ca, Ni, Cr or Al for Fe and Mg	Alteration	commonly alters to iddingsite and chlorophaeite, which are really mixtures of various minerals which cannot be identified, and serpentine. Alteration progresses from the edge and along cracks
Occurrence	pure Fo (Mg-rich) is restricted to metamorphosed carbonates, intermediate Fe-Mg olivine is common in mafic and ultramafic igneous rocks, Fe-rich olivine occurs in felsic rocks.	Distinguishing Features	high birefringence, distinctive fracturing, lack of cleavage, and alteration products.