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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.

Fluorite

var. yttrofluorite - #PD40419
Locality
Hundholmen, Tysfjord, Nordland, Norway 
Formula
CaF2 
Availability
Sold
Size
7 x 4 x 4 cm - Sm Cabinet 
Tagged
pegmatite mineral  

A yellowish mass of crystalline Fluorite rich in Yttrium. It comes with a few old University of Utah labels.


Fluorite

Formula
CaF2 
Crystal System
Isometric 
Crystal Habit
Crystalline - Coarse, Massive - Granular, Disseminated 
Cleavage
Three perfect, octahedral cleavages. 
Luster
Vitreous (Glassy) 
Color
purple, clear, yellow, green, red, blue 
Streak
white 
Geological Setting
Occurs in a wide range of geologic environments including low temperature Missississippi Valley lead-zinc deposits, hydrothermal gold deposits, Alpine cleft metamorphic environments  
Class
Isometric - Hexoctahedral 
Fracture
Uneven 
Hardness
Collection
Phillips Collection
Mineralpedia
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On Dakota Matrix
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Hureaulite - 40440
Hureaulite - 40440

Hureaulite

with Jahnsite-(CaMnMg) - #40440
Locality
Tip Top mine, Custer Co., South Dakota, United States 
Formula
Mn2+5(PO4)2(PO3OH)2·4H2
Availability
Sold
Size
6 x 4 x 3 cm - Sm Cabinet 
Tagged
phosphate , pegmatite mineral  

Salmon pink crystals of Hureaulite to 7mm on Jahnsite. The Tip Top mine is a granitic differentiated-zoned pegmatite with rare elements lithium and beryllium. Primary phosphates occur as large nodules which were later attacked by metasomatic activity, which were probably derived from late-stage end-fluids.


Hureaulite

Formula
Mn2+5(PO4)2(PO3OH)2·4H2
Crystal System
Monoclinic 
Crystal Habit
Massive, Compact, Fibrous 
Cleavage
Distinct, None, None 
Luster
Vitreous - Greasy 
Color
red, white, grayish white, yellowish white, reddish white 
Streak
white 
Class
Monoclinic - Prismatic 
Fracture
Brittle - Uneven 
Hardness

Hurlbutite

#PD40417
Locality
Viitaniemi pegmatite, Eräjärvi area, Orivesi, Etelä-Suomen Lääni, Finland 
Formula
CaBe2P2O8 
Availability
Sold
Size
6 x 4.5 x 3 cm - Sm Cabinet 
Tagged
phosphate , beryllium , pegmatite mineral  

The gray crystalline areas are the Hurlbutite - beryllium phosphate. The Viitaniemi pegmatite is phosphate rich and is classified as a LCT-type granitic pegmatite according to Mindat.


Hurlbutite

Formula
CaBe2P2O8 
Crystal System
Monoclinic 
Crystal Habit
Prismatic 
Cleavage
None, None, None 
Luster
Vitreous - Greasy 
Color
colorless, greenish white, yellow 
Streak
white 
Class
Monoclinic - Prismatic 
Fracture
Brittle - Conchoidal 
Hardness
Collection
Phillips Collection

Hydroxylherderite

on Microcline - #BM39976
Locality
Sabsar, Skardu dist., Baltistan, Gilgit-Baltistan, Pakistan 
Formula
CaBePO4(OH) 
Availability
Sold
Size
6 x 5 x 4 cm - Sm Cabinet 
Tagged
phosphate , beryllium , pegmatite mineral  

I would be remiss to not include a pegmatite mineral from Pakistan. So, a pale green 2cm nice crystal on Microcline.


Hydroxylherderite

Formula
CaBePO4(OH) 
Crystal System
Monoclinic 
Cleavage
Indistinct, None, None 
Luster
Vitreous (Glassy) 
Color
blue, blue green, colorless, greenish white, white 
Streak
white 
Class
Monoclinic - Prismatic 
Fracture
Sub Conchoidal 
Hardness
5-5.5 
Collection
McConlogue Collection

Jahnsite-(Nafemg)

with Leucophosphite - #40565
Locality
Tip Top mine, Custer Co., South Dakota, United States 
Formula
NaFe3+Mg2Fe3+2(PO4)4(OH)2·8H2
Availability
Sold
Size
3.5 x 2 x 2 cm - Miniature 
Tagged
phosphate , pegmatite mineral  
Special Info
Type Locality 
Special Info
XRD Confirmed 
Special Info
EDS Confirmed 
Special Info
Author's Material 

Several yellow, twinned, prismatic crystals of Jahnsite-(NaFeMg), the most recent new mineral from the Tip Top mine. It is a portion of the material used for the study, author's material, discovered by myself. The crystals are about 0.5mm with orange tips. There are probably 7 or 8 crystals in the photos shown and a few more on the backside. It occurs with dark purple Leucophosphite, Laueite, and Dufrenite.


Jahnsite-(Nafemg)

Formula
NaFe3+Mg2Fe3+2(PO4)4(OH)2·8H2
Crystal System
Monoclinic 
Crystal Habit
Prismatic, Striated 
Luster
Vitreous (Glassy) 
Color
yellow 
Streak
white 
Class
Monoclinic - Prismatic 
Fracture
Brittle - Splintery 
Hardness
Special Info
Type Locality
Special Info
XRD Confirmed
Special Info
EDS Confirmed
Special Info
Author's Material

Kosnarite

#PD40410
Locality
Mount Mica quarry, Paris, Oxford Co., Maine, United States 
Formula
KZr2(PO4)3 
Availability
Sold
Size
1 x 0.7 x 0.7 cm - Thumbnail 
Tagged
phosphate , pegmatite mineral  
Special Info
Type Locality 

There are not too many zirconium phosphates on Earth. Maine has two of the localities, this one, Mount Mica, is the type locality. The specimen is small and in the photos you can easily see one of the cubes. It is trigonal and crystallizes as pseudocubes. The crystal at the arrow is about 0.5mm but there are about 8 or 9 of them in a cluster not too easily seen in the photos. It is etched out according to the stick on label on the plastic box.


Kosnarite

Formula
KZr2(PO4)3 
Crystal System
Trigonal 
Cleavage
Perfect, None, None 
Luster
Vitreous (Glassy) 
Color
colorless, gray blue, light green 
Streak
white 
Class
Trigonal - Hexagonal Scalenohedral 
Hardness
4.5 
Collection
Phillips Collection
Special Info
Type Locality
Mineralpedia
View Kosnarite
On Dakota Matrix
Previously Sold Kosnarite
On Dakota Matrix
Other Available Kosnarite
WebMineral
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Mindat
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