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Bastnäsite

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MGR715674

Bastnäsite

Description Tabs

Description
Locality: 
Zagi Mountain, Federally Administered Tribal Areas, Pakistan
Class: 
Crystals on Matrix
Size Range: 
Thumbnail (1-3cm)
Size: 
2.8 × 2.1 × 1.5 cm
Description

Bastnäsite is generally rare, the best, most well developed and largest crystals in the best quality are from Zagi Mts. (type locality is Bastnäs Mine in Sweden – from there we know only tiny crystals). This mineral exist in yellow, brown and red-brown color and crystals are hexagonal. France produced nice quality – gemmy, yellow crystals, but only 2 to 3mm. All other localities world-wide produce only micro-crystals. Only exception is Proudette Quarry in Quebec, Canada. This famous locality also produce crystals in 1cm size or even larger, but they never reach the quality of material from Zagi Mts.
Now more about the locality: Zagi Mts are also an alpino-type locality and minerals come from clefts and veins, again hand-extracted from local field-collectors. These veins and clefts are hosted in alkaline granite gneiss of the Warsak igneous complex. The area is about 15km in square, so a relatively small locality. It is easy to reach in a geographical meaning, only 40km distance to Peshawar. But the situation there is too dangerous to go there for digging and Bastnäsite is rare and difficult to find.
The particular specimen is really fine – it shows two crystals (main crystal is 12mm across) on matrix, matrix pieces are more uncommon. The crystals are sharp, both around 1cm tall (good dimension for the mineral), they show excelent luster and dark intense color. They are more gemmy and transparent in person! Again – Bastnäsite is usually hexagonal – also the upper main crystal shows a hexagonal diameter, but uncommon modifications at the end points. The second (lower) crystal is completely crazy. It is twinned and the habit is very complex with lot of modifications. The contrast with snowy white Adularia is very nice and finally you can find thin elongated quartz crystals in green color (caused by Chlorite inclusions).

Mineral Data
What's on the rock

Bastnäsite

Synonym Of: 

Bastnäsite-(Ce)

Formula: 
(Ce,La)(CO3)F
Strunz: 
5.BD.20a
Hardness: 
4.0 - 4.5

Bastnäsite-(La)

Formula: 
(La,Ce)(CO3)F
Strunz: 
5.BD.20a
Hardness: 
4.0 - 5.0

Bastnäsite-(Nd)

Formula: 
Nd(CO3)F
Strunz: 
5.BD.20a
Hardness: 
4.0 - 4.5

Bastnäsite-(Y)

Formula: 
(Y,Ce)(CO3)F
Strunz: 
5.BD.20a
Hardness: 
4.0 - 4.5