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Feldspars & Feldspathoids

Friday, 18 August 2017 12:30 PM

Feldspars are found in nearly every geological environment. We will have a nice group feldspars and feldspathoids which represents these diverse deposits.

Afghanite

#25149
Locality
Vetralla, Viterbo Prov., Lazio, Italy 
Formula
Na22Ca10(Si24Al24)O96(SO4)6Cl6 
Availability
Available
Price
$25.00
Size
4.5 x 4.5 x 4 cm - Miniature 

Tiny, less than 1mm, euhedral crystals deep in vug. Poor photos. Afghanite is a feldspathoid.


Afghanite

Formula
Na22Ca10(Si24Al24)O96(SO4)6Cl6 
Crystal System
Hexagonal 
Crystal Habit
Massive 
Cleavage
Perfect, None, None 
Luster
Vitreous (Glassy) 
Color
blue, colorless 
Streak
white 
Class
Hexagonal 
Fracture
Conchoidal 
Hardness
5.5-6 
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Albite

var. pericline - #PD46624
Locality
South Tyrol, Trentino, Italy 
Formula
NaAlSi3O8 
Availability
Sold
Size
10 x 5 x 4 cm - Cabinet 

Pericline crystal group with white glossy crystals to 2cm. The crystals are elongated by twinning on the b-axis with long inclined faces along the prism.


Albite

Formula
NaAlSi3O8 
Crystal System
Triclinic 
Crystal Habit
Blocky, Striated, Granular 
Cleavage
Perfect, Good, None 
Luster
Vitreous (Glassy) 
Color
white, gray, greenish gray, bluish green, gray 
Streak
white 
Class
Triclinic - Pinacoidal 
Fracture
Uneven 
Hardness
Collection
Phillips Collection
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Albite

Anorthite series var. labradorite - #DH47311
Locality
Woodward Ranch, Alpine, Brewster Co., Texas, United States 
Formula
NaAlSi3O8 
Availability
Available
Price
$40.00
Size
2 x 1 x 0.8 cm - Thumbnail 
Special Info
Gem Quality 

Light yellow gemmy labradorite. This material has weathered out of basalts. This labradorite has no schiller effect since there there are probably no exsolved layering which causes the labradorescence (schiller).


Albite

Formula
NaAlSi3O8 
Crystal System
Triclinic 
Crystal Habit
Blocky, Striated, Granular 
Cleavage
Perfect, Good, None 
Luster
Vitreous (Glassy) 
Color
white, gray, greenish gray, bluish green, gray 
Streak
white 
Class
Triclinic - Pinacoidal 
Fracture
Uneven 
Hardness
Collection
Dr. David Hess Collection
Special Info
Gem Quality
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Albite

var. oligoclase, sunstone - #PD47334
Locality
Arendal, Aust-Agder, Norway 
Formula
NaAlSi3O8 
Availability
Available
Price
$45.00
Size
7 x 5 x 2 cm - Sm Cabinet 
Special Info
Antique Specimen 

Not much of a specimen but with two old lables, it's a nice score. This is a variety of Albite called oligoclase, which should contain at least 70% Na, so very close to end member Albite. Tilting this specimen back and forth you will see tiny reflections of oriented hematite crystals withing the oligoclase. This property is gives the name "sunstone" to some oligoclase.


Albite

Formula
NaAlSi3O8 
Crystal System
Triclinic 
Crystal Habit
Blocky, Striated, Granular 
Cleavage
Perfect, Good, None 
Luster
Vitreous (Glassy) 
Color
white, gray, greenish gray, bluish green, gray 
Streak
white 
Class
Triclinic - Pinacoidal 
Fracture
Uneven 
Hardness
Collection
Phillips Collection
Special Info
Antique Specimen
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Albite

var. pericline - #DS47343
Locality
Pfitsch Tal, Tyrol, Austria 
Formula
NaAlSi3O8 
Availability
Sold
Size
6 x 5.5 x 3 cm - Sm Cabinet 

This is a variety of Albite, known as pericline, taking its name from the Greek word, periklinis, or inclined on all sides (Mindat).  Pericline is the variety of Albite with a glazed porcelain-like luster and milky white color. Pericline is elongated and twinned along the b-axis and thus have long tapering faces along the prism form.

Note old lables in prov. tab.


Albite

Formula
NaAlSi3O8 
Crystal System
Triclinic 
Crystal Habit
Blocky, Striated, Granular 
Cleavage
Perfect, Good, None 
Luster
Vitreous (Glassy) 
Color
white, gray, greenish gray, bluish green, gray 
Streak
white 
Class
Triclinic - Pinacoidal 
Fracture
Uneven 
Hardness
Collection
Shultz Collection
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Albite

var. pericline - #PD47344
Locality
Saflisch Valley, Binn Valley, Wallis, Switzerland 
Formula
NaAlSi3O8 
Availability
Sold
Size
11 x 10 x 7 cm - Cabinet 

Lustrous white elongated crystals to 1.4cm.


Albite

Formula
NaAlSi3O8 
Crystal System
Triclinic 
Crystal Habit
Blocky, Striated, Granular 
Cleavage
Perfect, Good, None 
Luster
Vitreous (Glassy) 
Color
white, gray, greenish gray, bluish green, gray 
Streak
white 
Class
Triclinic - Pinacoidal 
Fracture
Uneven 
Hardness
Collection
Phillips Collection
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