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THE MINERAL ANGLESITE


Anglesite is a rare lead mineral and can be a beautiful specimen. The typically high luster associated with lead minerals makes them sparkle like gemstones and Anglesite is no exception to the rule. Anglesite's yellow color seen in many specimens is attractive and adds to the specimen's appeal. Anglesite has the same structure as barite (BaSO 4 ) and forms very similar crystals. However, Anglesite has a very high density and even though Barite is a rather heavy mineral, Anglesite is nearly 50% more dense.

Anglesite is named for its type locality of Anglesey, an island at the northern tip of the United Kingdom.  It is a secondary mineral, typically formed in the oxidation zone of galena (lead sulfide) ores.

PHYSICAL CHARACTERISTICS:

  • Color is usually colorless, white and yellow; also pale gray, blue and green.
  • Luster is adamantine.
  • Transparency crystals are transparent to translucent.
  • Crystal System is orthorhombic; 2/m 2/m 2/m
  • Crystal Habits include the bladed or tabular crystals that are dominated by two large pinacoid faces top and bottom and small prism faces forming a jutting angle on every side. There are many variations of these faces and complex forms can occur. If the pinacoid faces become diminished or are absent, the resulting prismatic crystal has a rhombic cross section.. Anglesite typically forms a flattened blade that juts out from a host rock and with what appears to be a steep dome termination but is actually two faces of another rhombic prism. Also forms crusts and is granular and massive.
  • Cleavage is perfect in one direction, less so in two other directions.
  • Fracture is conchoidal.
  • Hardness is 2.5 - 3.
  • Specific Gravity is approximately 6.3+ (very heavy for translucent minerals)
  • Streak is white.
  • Associated Minerals are galena, cerussite, barite and limonite.
  • Other Characteristics: Index of refraction is 1.88+ (very high), some specimens fluoresce yellow under UV light.
  • Notable Occurances include Tsumeb, Nambia; Australia; England, Mexico and Toussit, Morocco.
  • Best Field Indicators are crystal habit, density, high luster and color.

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