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Pegmatite Minerals

Friday, 31 October 2014 06:00 PM

Pegmatites are located all over the world and have have produced not only ore minerals but scientifically important rare mineral species. We will take a look at these minerals, mostly rare species, as well as introduce you to the many complexities of these interesting geological deposits.

SOLD
Bityite - BM40514
Bityite - BM40514

Bityite

#BM40514
Locality
Maharitra, Sahatany Pegmatite Field, Mt Ibity area, Antananarivo, Madagascar 
Formula
CaLiAl2(Si2BeAl)O10(OH)2 
Availability
Sold
Size
5 x 2.5 x 2 cm - Miniature 
Tagged
beryllium , pegmatite mineral  

This is actually a very good specimen showing colorless or creamy, thick hexagonal plates.

One of a handful of lithium micas and the only one with essential beryllium. More information about micas can be found in this article:  Micas and other Phyllosilicates. It is chiefly a pegmatite mineral.


Bityite

Formula
CaLiAl2(Si2BeAl)O10(OH)2 
Crystal System
Monoclinic 
Crystal Habit
Encrustations, Platy, Pseudo Hexagonal 
Cleavage
Perfect, None, None 
Luster
Vitreous (Glassy) 
Color
brown white, colorless, yellow, pearl white 
Streak
white 
Class
Monoclinic - Prismatic 
Hardness
5.5 
Collection
McConlogue Collection
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Bjarebyite

#PD40415
Locality
Palermo mine, Groton, Grafton Co., New Hampshire, United States 
Formula
BaMn2+2Al2(PO4)3(OH)3 
Availability
Sold
Size
1 x 1 x 1 cm - Thumbnail 
Tagged
phosphate , pegmatite mineral  
Special Info
Type Locality 

This is an exceptional specimen of Bjarebyite, a mineral which can easily be confused with Perloffite or even Dickinsonite (now an Arrojadite). The cluster here is 2mm, terminated and is a dark green.


Bjarebyite

Formula
BaMn2+2Al2(PO4)3(OH)3 
Crystal System
Monoclinic 
Crystal Habit
Acicular, Striated, Prismatic 
Cleavage
Perfect, Perfect, None 
Luster
Subadamantine 
Color
emerald green 
Streak
white 
Class
Monoclinic - Prismatic 
Hardness
Collection
Phillips Collection
Special Info
Type Locality

Bohmite

with Thomsonite - #PD40475
Locality
Saga quarry, Sagåsen, Mørje, Porsgrunn, Telemark, Norway 
Formula
AlO(OH) 
Availability
Sold
Size
3.5 x 3 x 3 cm - Miniature 
Tagged
pegmatite mineral  

Light brown platy crystals and white acicular crystals of Thomsonite.


Bohmite

Collection
Phillips Collection
Mineralpedia
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Brazilianite

#PD40491
Locality
Newport, Sullivan Co., New Hampshire, United States 
Formula
NaAl3(PO4)2(OH)4 
Availability
Sold
Size
5 x 4 x 4 cm - Miniature 
Tagged
phosphate , pegmatite mineral  

Light yellowish green lustrous 1-3mm crystals in a 2.5cm vug. Comes with a Paul Moore tag form Phillips collection with a number matching the specimen to the label.


Brazilianite

Formula
NaAl3(PO4)2(OH)4 
Crystal System
Monoclinic 
Crystal Habit
Spherical, Euhedral Crystals 
Cleavage
Good, None, None 
Luster
Vitreous (Glassy) 
Color
colorless, greenish yellow, yellow green, light yellow 
Streak
white 
Class
Monoclinic - Prismatic 
Fracture
Conchoidal 
Hardness
5.5 
Collection
Phillips Collection

Chiavennite

with Helvine, Natrolite & Analcime - #PD40474
Locality
Tvedalen, Larvik, Vestfold, Norway 
Formula
CaMn2+(BeOH)2Si5O13·2H2
Availability
Sold
Size
5.5 x 5 x 4 cm - Sm Cabinet 
Tagged
beryllium , pegmatite mineral  

A rich specimen of orange, rosette-like crystals of Chiavennite to around .75mm. It is an orthorhombic beryllium zeolite. Outside of the Larvik area, it is only found in 3 or 4 other localities worldwide, all pegmaites.

The Langesundsfjord area hosts some of the world's most mineralogically diverse nepheline syenite pegmatites. The host rock is the silica poor Larvikite, a monzonitic rock, which is used as a local building stone.

This specimen also contains numerous amber colored Helvine (red arrows) crystals to 1mm. I don't think these are Wickmanite or Tetrawickmanite. Zircons are also present as well as tiny colorless Analcime crystals and prismatic Natrolite. It is an excellent specimen.


Chiavennite

Formula
CaMn2+(BeOH)2Si5O13·2H2
Crystal System
Orthorhombic 
Cleavage
Perfect, None, None 
Luster
Vitreous (Glassy) 
Color
yellow, orange, red orange 
Streak
white 
Class
Orthorhombic - Dipyramidal 
Hardness
Collection
Phillips Collection

Clinobisvanite

#PD40500
Locality
Londonderry Lithium deposit, Western Australia, Australia 
Formula
BiVO4 
Availability
Sold
Size
6 x 5 x 4 cm - Sm Cabinet 

It may be surprising to you that most of the Clinobisvanite occurences are in pegmatites. It actually occurs at the Rock Ridge pegmatite in the Black Hills, at Pala, the Rubicon pegmatite in Erongo, and in lithium pegmatites of Japan, Mozambique, and Madagascar. Native Bismuth is common in pegmatites. The Bismuth must carry Vanadium as I don't know otherwise where it would come from.

In these photos all of the yellow staining is Clinobisvanite and halos a tiny 2mm Bismuth crystal.


Clinobisvanite

Formula
BiVO4 
Crystal System
Monoclinic 
Color
yellow, orange 
Class
Monoclinic - Prismatic 
Hardness
Collection
Phillips Collection

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