Bytownite (a variety of Feldspar)
Current inventory:  0 gems
 

  
Bytownite is named for Bytown (now Ottawa), Canada, where it was discovered.

Discovered in 1835;   IMA status:  Not Valid (intermediate member of the Plagioclase Series)

Chemistry

Chemical Formula:

(Ca,Na)(Si,Al)₄O₈

Calcium Sodium Aluminum Silicate

Molecular Weight:

275.01 gm

Composition:

Sodium

1.67 %

Na

2.25 %

Na₂O

Calcium

11.66 %

Ca

16.31 %

CaO

Aluminum

17.66 %

Al

33.37 %

Al₂O₃

Silicon

22.47 %

Si

48.07 %

SiO₂

Oxygen

46.54 %

O

100.00 %

100.00 %

= TOTAL OXIDE

Classification

Mineral Classification:

Silicates (Germanates)

Strunz 8th Ed. ID:

8/J.07-60

Nickel-Strunz 10th Ed. ID:

9.FA.35

9 : SILICATES (Germanates)
F : Tektosilicates without zeolitic H₂O
A : Tektosilicates without additional non-tetrahedral anions

Related to:

Feldspar Group. Plagioclase Series. A variety of Anorthite.

Members of Group:

Feldspar Group: Albite, Andesine, Anorthoclase, Banalsite, Buddingtonite, Bytownite, Celsian, Dmisteinbergite, Hyalophane, Labradorite, Microline, Oligoclase, Orthoclase, Paracelsian, Reedmergnerite, Sanidine, Slawsonite, Stronalsite, Svyatoslavite

Varieties:

None

Synonyms:

None

Crystal Data

Crystallography:

Triclinic - Pinacoidal

Crystal Habit:

Crystals are rare; flattened, to 3 cm; commonly as cleavable masses or anhedral grains in massive aggregates.

Twinning:

Common after the Albite, Carlsbad, and Pericline laws, developed in simple to complex combinations.

Physical Properties

Cleavage:

Perfect on {001}, Good on {010}, Imperfect on {110}

Fracture:

Irregular/Uneven, Step-Like

Tenacity:

Brittle

Moh's Hardness:

6.0 - 6.5

Density:

2.72 - 2.75 (g/cm³)

Luminescence:

None

Radioactivity:

Not Radioactive

Optical Properties

Color:

Colorless, White, Gray, Pale Yellow

Transparency:

Transparent to Translucent

Luster:

Vitreous, Pearly on cleavages

Refractive Index:

1.563 - 1.585  Biaxial ( - )

Birefringence:

0.0100 - 0.0110

Dispersion:

r > v, strong  (mindat.org)
r < v, weak  (Handbook of Mineralogy pdf)

Pleochroism:

None

Occurances

Geological Setting:

A rock-forming mineral typical of mafic intrusive igneous rocks, as gabbros and anorthosites; as phenocrysts in basalts; rare in metamorphic rocks.

Common Associations:

Pyroxenes, Olivine

Common Impurities:

None

Type Locality:

Ottawa (formerly Bytown), Gloucester Township, Carleton Co., Ontario, Canada

Year Discovered:

1835

View mineral photos:

Bytownite Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

Bytownite is a variety of Anorthite and is a rare member of the Plagioclase Series of the Feldspar Group of minerals that includes Albite, Amazonite, Andesine, Anorthite, Bytownite, Hyalophane, Labradorite, Moonstone, Oligoclase, Orthoclase, Sanidine and Sunstone. Bytownite is a bright and beautiful champagne colored gem. Most gem quality Bytownite crystals are currently coming from Chihuahua, Mexico and Grants District, New Mexico.

Bytownite is one of the less frequently identified feldspars, although still very common. The "type material" from Ottawa, Ontario, Canada was later shown to be a mixture. Elsewhere in Canada, from the Shawmere anorthosite, Foleyet Township, Ontario, and on Yamaska Mountain, near Abbotsford, Quebec. On Rhum Island, Scotland. At Eycott Hill, near Keswick, Cumberland, England. From Närödal, Norway. In Greenland, from Fiskenaesset and Storo. In the Bushveld complex, Transvaal, South Africa. In the USA, in the Stillwater complex, Montana; from Cornwall, Lebanon County, and Phoenixville, Chester County, Pennsylvania; near Lakeview, Lake County, Oregon; in the Lucky Cuss mine, Tombstone, Cochise County, Arizona; and from the Grants district, McKinley County, New Mexico. From Isa Valley, Western Australia.
 

  
Bytownite gems for sale:

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