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Minerals of Butte, Montana

Friday, 23 December 2016 06:00 PM

Mineral Specimens from the Butte District in Montana. Read all about Butte mining history, geology and minerals.

Azurite

on Malachite - #45855
Locality
Pittsmont mine, Bullwhacker pit, Silver Bow Park, Butte dist., Silver Bow Co., Montana, United States 
Formula
Cu3(CO3)2(OH)2 
Availability
Sold
Size
8 x 5.5 x 5.5 cm - Sm Cabinet 
Tagged
carbonate , copper  

Fine blue rosettes across face on Malachite. Chris van Laer states that this is from the Bullwhacker pit, Silver Bow Park, which was on the Continental fault of the Pittsmont mine.  Mindat # JF2-3EC. 


Azurite

Formula
Cu3(CO3)2(OH)2 
Crystal System
Monoclinic 
Crystal Habit
Tabular, Prismatic, Stalactitic 
Cleavage
Perfect, Fair, None 
Luster
Vitreous (Glassy) 
Color
azure blue, blue, light blue, dark blue 
Streak
light blue 
Class
Monoclinic - Prismatic 
Fracture
Brittle - Conchoidal 
Hardness
3.5-4 
Collection
Chris van Laer Collection
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Betekhtinite

with Bornite & Quartz - #45876
Locality
Butte dist., Silver Bow Co., Montana, United States 
Formula
(Cu,Fe)21Pb2S15 
Availability
Sold
Size
8 x 7 x 4 cm - Sm Cabinet 
Tagged
sulfide , copper  

The Betekhtinite is scarce on this specimen but very visible and can be seen as elongated steely gray prismatic crystals intimately associated with groups of tarnished Bornite groups to 8mm. The Quartz is nice and waterclear to 2cm some with included Hematite(?). 


Betekhtinite

Formula
(Cu,Fe)21Pb2S15 
Crystal System
Orthorhombic 
Crystal Habit
Acicular 
Cleavage
Distinct, Distinct, Distinct 
Luster
Metallic 
Color
brownish black 
Streak
black 
Class
Orthorhombic - Dipyramidal 
Hardness
Collection
Chris van Laer Collection

Calcite

#45853
Locality
Butte dist., Silver Bow Co., Montana, United States 
Formula
CaCO3 
Availability
Sold
Size
5.5 x 3 x 3.5 cm - Sm Cabinet 
Tagged
carbonate  

Elongated colorless to white nail-head Calcite crystals. This group is 3cm on another, earlier generation of Calcite.


Calcite

Formula
CaCO3 
Crystal System
Trigonal 
Crystal Habit
Crystalline - Coarse, Stalactitic, Massive 
Cleavage
Perfect, Perfect, Perfect 
Luster
Vitreous (Glassy) 
Color
colorless, white, pink, yellow, brown 
Streak
white 
Class
Trigonal - Hexagonal Scalenohedral 
Fracture
Brittle - Conchoidal 
Hardness
Collection
Chris van Laer Collection
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Chalcocite

#45922
Locality
4400' L, Steward mine, Butte dist., Silver Bow Co., Montana, United States 
Formula
Cu2
Availability
Sold
Size
5.5 x 4 x 1.5 cm - Sm Cabinet 
Tagged
sulfide , copper  

At first glance this does not appear like much of a specimen. But upon closer examination under a scope there are literally hundreds of 1-2mm, dull gray, Chalcocite crystals, some nicely twinned. 


Chalcocite

Formula
Cu2
Crystal System
Monoclinic 
Crystal Habit
Massive, Granular, Euhedral Crystals 
Cleavage
Indistinct, None, None 
Luster
Metallic 
Color
blue black, gray, black, black gray, steel gray 
Streak
grayish black 
Class
Monoclinic - Prismatic 
Fracture
Conchoidal 
Hardness
2.5-3 
Collection
Chris van Laer Collection

Chalcocite

with Pyrite & Tennantite - #45931
Locality
Butte dist., Silver Bow Co., Montana, United States 
Formula
Cu2
Availability
Sold
Size
4.5 x 2.5 x 2.5 cm - Miniature 
Tagged
sulfide , copper  

The largest crystal is 9x6mm, most of the other crystals are between 1 to 3mm. All of the Chalcocite crystals are well-defined but a bit unusual as they are not your classic shape for Chalcocite. Chris van Laer was a little hesitant to call these Chalcocite. The matrix is composed of micro Pyrite with some dull black blebs of Tennantite(?).


Chalcocite

Formula
Cu2
Crystal System
Monoclinic 
Crystal Habit
Massive, Granular, Euhedral Crystals 
Cleavage
Indistinct, None, None 
Luster
Metallic 
Color
blue black, gray, black, black gray, steel gray 
Streak
grayish black 
Class
Monoclinic - Prismatic 
Fracture
Conchoidal 
Hardness
2.5-3 
Collection
Chris van Laer Collection

Chalcocite

with Pyrite - #45932
Locality
Butte dist., Silver Bow Co., Montana, United States 
Formula
Cu2
Availability
Available
Price
$75.00
Size
5 x 3.5 x 2.5 cm - Miniature 
Tagged
sulfide , copper  

Dull, black partial Chalcocite crystals to 2mm and formless "blebs" occur all over this specimens on the Pyrite and within the Quartz crystals. It is not the most aestheic specimen but is typical for Butte.


Chalcocite

Formula
Cu2
Crystal System
Monoclinic 
Crystal Habit
Massive, Granular, Euhedral Crystals 
Cleavage
Indistinct, None, None 
Luster
Metallic 
Color
blue black, gray, black, black gray, steel gray 
Streak
grayish black 
Class
Monoclinic - Prismatic 
Fracture
Conchoidal 
Hardness
2.5-3 
Collection
Chris van Laer Collection

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