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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
Petersenite-(Ce) - PD40457
Petersenite-(Ce) - PD40457

Petersenite-(Ce)

#PD40457
Locality
Koashva Mt., Khibiny Massif, Kola Peninsula, Russia 
Formula
Na4(Ce,La,Nd)2(CO3)5 
Availability
Sold
Size
1.5 x 0.5 x 0.7 cm - Thumbnail 
Tagged
carbonate , REE mineral , pegmatite mineral  

Tiny, less than 1mm, very thin, acicular crystals in vuggy mass. Koashva is a hyperalkaline or hyperagpaitic (low Al, high sodium) pegmatite.


Petersenite-(Ce)

Formula
Na4Ce2(CO3)5 
Crystal System
Monoclinic 
Crystal Habit
Prismatic, Acicular 
Cleavage
None, None, None 
Luster
Vitreous (Glassy) 
Color
light violet, light yellow, pink gray, reddish gray 
Streak
white 
Class
Monoclinic - Sphenoidal 
Fracture
Brittle - Conchoidal 
Hardness
Collection
Phillips Collection
SOLD
Pollucite - 39072
Pollucite - 39072

Pollucite

#39072
Locality
Tanco pegmatite, Bernic Lake, Manitoba, Canada 
Formula
Cs(Si2Al)O6·nH2
Availability
Sold
Size
4 x 3.5 x 3 cm - Miniature 
Tagged
REE mineral , pegmatite mineral  

Colorless to white crystalline mass of Pollucite from the largest Pollucite deposit known.


Pollucite

Formula
Cs(Si2Al)O6·nH2
Crystal System
Isometric 
Crystal Habit
Massive 
Cleavage
None, None, None 
Luster
Vitreous - Dull 
Color
colorless, white, gray, pale pink, blue 
Streak
white 
Class
Isometric - Hexoctahedral 
Fracture
Brittle - Uneven 
Hardness
6.5 

Pollucite

#PD40441
Locality
Buckfield, Oxford Co., Maine, United States 
Formula
Cs(Si2Al)O6·nH2
Availability
Sold
Size
6.5 x 5 x 2.5 cm - Sm Cabinet 
Tagged
REE mineral , pegmatite mineral  

A white to colorless crystalline mass. Maine pegmatites are granitic LCT-type (Lithium-cesium-tantalum), that is rich in these elements which form minerals such as this one, Pollucite.

Dr. Van King wrote an tremendously informative article for Rocks and Minerls Nov/Dec 1987 in which he describes general pegmatite geology but also Maine pegmatite characteristics. King also wrote a book called "A Collector's Guide to Granitic Pegmatites", an excellent introduction to pegmatites.

Ex. Cooke specimen, acquired through Dakota Matrix and then by Bill McConlogue.

Cerny, one of our foremost pegmatite experts, in 1982 contributed papers to the Min. Assoc. of Canada Short Course on Granitic Pegmatites. He describes the occurence of Pollucite in pegmatites as originating as a primary contituent from residual fluids or as a late stage metasomatic product. Very few granitic pegmatites as a percent contain Pollucite. The largest deposit is Tanco in Manitoba.


Pollucite

Formula
Cs(Si2Al)O6·nH2
Crystal System
Isometric 
Crystal Habit
Massive 
Cleavage
None, None, None 
Luster
Vitreous - Dull 
Color
colorless, white, gray, pale pink, blue 
Streak
white 
Class
Isometric - Hexoctahedral 
Fracture
Brittle - Uneven 
Hardness
6.5 
Collection
Phillips Collection
SOLD
Pollucite - 18916
Pollucite - 18916

Pollucite

#18916
Locality
Skardu dist., Balistan, Northern Areas, Pakistan 
Formula
Cs(Si2Al)O6·nH2
Availability
Sold
Size
6 x 5 x 2 cm - Sm Cabinet 
Tagged
REE mineral , pegmatite mineral  

A large mass of olorless, crystalline Pollucite.


Pollucite

Formula
Cs(Si2Al)O6·nH2
Crystal System
Isometric 
Crystal Habit
Massive 
Cleavage
None, None, None 
Luster
Vitreous - Dull 
Color
colorless, white, gray, pale pink, blue 
Streak
white 
Class
Isometric - Hexoctahedral 
Fracture
Brittle - Uneven 
Hardness
6.5 

Rinkite

with Amphibole - #PD40481
Locality
Barkevik, Langesundsfjorden, Larvik, Vestfold, Norway 
Formula
Na2(Na,Ca)(Ca,Ce)4Ti(Si2O7)2OF3 
Availability
Sold
Size
7 x 6 x 4 cm - Sm Cabinet 
Tagged
REE mineral  

Dark brown segregations in plagioclase matrix. Originally labeled as "johnstrupite", which is now considered a variety of Rinkite with a similar chemistry per Mindat.

Brøgger, a famous Norwegian mineralogist who laid the foundation of nepheline syenite pegmatites in his landmark monograph: “Die Mineralien der Syenitpegmatitgänge der südnorwegischen Augit- und Nephelinsyenite” (The mineralogy of syenite pegmatites of souther Norway). It would be nice to get the English translation of this 950 page study.

 


Rinkite

Formula
Na2(Na,Ca)(Ca,Ce)4Ti(Si2O7)2OF3 
Crystal System
Monoclinic 
Crystal Habit
Prismatic, Tabular 
Cleavage
Good, None, None 
Luster
Vitreous (Glassy) 
Color
yellow, yellowish green, brown 
Streak
yellow white 
Class
Monoclinic - Sphenoidal 
Hardness
Collection
Phillips Collection
Mineralpedia
View Rinkite
On Dakota Matrix
Previously Sold Rinkite
On Dakota Matrix
Other Available Rinkite
WebMineral
View Rinkite
Mindat
View Rinkite

Robertsite

#40493
Locality
Tip Top mine, Custer Co., South Dakota, United States 
Formula
Ca2Mn3+3O2(PO4)3·3H2
Availability
Sold
Size
8 x 6 x 2 cm - Sm Cabinet 
Tagged
phosphate , pegmatite mineral  
Special Info
Type Locality 
Special Info
XRD Confirmed 
Special Info
EDS Confirmed 

Long, deep red bladed Robertsite (XRD) possibly phasing into Mitridatite. Robertsite will usually be found as stubby little deep red crystals at the Tip Top. On this specimen, the Robertsite forms plates to 2mm. There is some late-stage apatite probably a product of weathering. Quartz matrix with layers of lavender carbonate apatite.


Robertsite

Formula
Ca2Mn3+3O2(PO4)3·3H2
Crystal System
Monoclinic 
Crystal Habit
Aggregates, Felted 
Cleavage
Good, None, None 
Luster
Adamantine 
Color
blood red, brownish black, dark red, reddish brown, black 
Streak
brown 
Class
Monoclinic - Prismatic 
Hardness
3.5 
Special Info
Type Locality
Special Info
XRD Confirmed
Special Info
EDS Confirmed

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