Mineral Information and Data:

Alstonite
BaCa(CO3)2 [CNMNC approved formula]

Named from the locality: Brownley Hill lead mine, Alston, Cumberland and Fallowfield lead mine hear Hexham, Northcumberland, England.

IMA status : Valid species (Pre-IMA 1841) Grandfathered
CLASSIFICATION 
Dana
(8th edition) :
14.02.05.01  
  (14) Anhydrous Carbonates
  (14.02) with Compound Formula A+ B++ (CO3)2
  (14.02.05)
  
Nickel-Strunz
(10th edition) :
05.AB.35
  (05) Carbonates and Nitrates
  (05.A) Carbonates without additional anions, without H2O
  (05.AB) Alkali-earth (and other M2+) carbonates
  
Crystal system: Triclinic System
Point group (H-M): 1 — pedial
Unit cell: a = 17.36 Ǻ, b = 14.40 Ǻ, c = 6.12 Ǻ, a = 90.4°, b = 90.1°, g = 120.1°
Crystal Habit: Crystals commonly twinned; as pseudo-hexagonal prisms, pseudo-hexahagonal dipyramids.
Twinning: on {110}or {130}
  
Color: Colorless, white, grayish, pink
Diaphaneity: Transparent to translucent
Luster: Vitreous
Hardness (Mohs): 4 - 4.5
Measured Density: 3.707 g/cm3
Cleavage: 1; {110} imperfect
Fracture: Uneven
Streak: White
  
Polymorphism and Series: Trimorphous with barytocalcite and paralstonite.
Geologic Setting: Typically in low-temperature hydrothermal Pb–Zn deposits; rare in carbonatites.
Mineral Association: Calcite, barite, ankerite, siderite, benstonite, galena, sphalerite, pyrite, quartz
  

 

Alstonite
Alstonite on barite rich matrix
Origin: Brownley Hill mine, Nenthead, Cumbria, England
Sample size: 6.5 x 4 x 3.2 cm
Photo: Dan Weinrich

 

Alstonite
(zoom-in of above)

 

Alstonite
Alstonite on witherite
Origin: Brownley Hill (Bloomsberry) Mine, Nenthead,
Alston Moor, Cumbria, England (cotype locality)
Sample size: 4 x 3 x 3 cm
Photo: Rob Lavinsky

 

Alstonite
(zoom-in of above)

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