THE MINERAL MIXITE


Mixite is one of just a handfull of bismuth minerals and one of even fewer bismuth arsenates. Other bismuth arsenates include walpurgite and atelestite, to name a couple. Mixite is probably the best known of these, but is still a rare mineral by most considerations. It forms in the oxidation zone of metal ores that probably contained primary bismuth sulfides such as emplectite.

As a mineral collection specimen, mixite is truly a wonderful addition. It forms nice radial clusters called spherules, made up of fine acicular crystals. The color is typically a brilliant green of one shade or another coupled with an attractive silky luster.

Mixite lends its name to a small group of rather obscure minerals called the Mixite Group. The Mixite Group is a group of hexagonal, hydrated copper arsenate and phosphate hydroxides with a general formula of ACu6(XO4)3(OH)6 - 3H2O The A in the formula can be either bismuth, aluminum, calcium, cerium, lanthanum, yttrium, neodymium or thorium. The X can be either arsenic or phosphorous.

These are the members of the Mixite Group:

  • Agardite (Hydrated Lanthanum Yttrium Calcium Cerium Neodymium Copper Arsenate Hydroxide)
  • Goudeyite (Hydrated Aluminum Yttrium Copper Arsenate Hydroxide)
  • Mixite (Hydrated Bismuth Copper Arsenate Hydroxide)
  • Petersite (Hydrated Yttrium Calcium Copper Phosphate Hydroxide)

Agardite actually represents at least a couple of minerals and is sometimes considered a mineral group itself. Agardite and mixite are difficult to differentiate. But if the specimen is associated with other bismuth minerals, than this can prove diagnostic in mixite's favor.

PHYSICAL CHARACTERISTICS:

  • Color is green, emerald-green, blue-green, yellow-green or off-white.
  • Luster is vitreous or silky to dull.
  • Transparency: Crystals are transparent to translucent.
  • Crystal System is hexagonal.
  • Crystal Habits include radiating clusters, tufts or spherules of acicular or fibrous crystals, also massive, capillary and earthy.
  • Cleavage not noticeable.
  • Fracture is fibrous.
  • Hardness is 3 - 4.
  • Specific Gravity is approximately 3.8 - 4.0 (above average for translucent minerals).
  • Streak is light green.
  • Associated Minerals are pharmacosiderite, zeunerite, emplectite, limonite, malachite, wulfenite, mimetite and barite.
  • Notable Occurrences include Germany; El Carmen Mine, Durango, Mexico; France; Jachymov of the former Czechoslovakia; Inyo County, California and Gila and Pinal Counties in Arizona, USA.
  • Best Field Indicators are color, crystal habit, density and associations with bismuth ores.
This Site Awarded
Available MIXITE specimens:
see this List of ALL specimens including SOLD ones

 

Copyright ©1995-2014 by Amethyst Galleries, Inc.
Site design & programming by galleries.com web services