Ontario Mineral - Galena

 
Chemistry:
 PbS, Lead Sulfide
Class:
 Sulfides
Subclass:
  
Group:
 Galena
Uses:
 Major ore of lead and silver
Color:
 lead to silver gray sometimes with a bluish tint
Luster:
 metallic to dull in weathered faces
Transparency:
 crystals are opaque
Crystal System:
 isometric; 4/m bar 3 2/m
Crystal Habits:
 include the cube, octahedron and combinations of the two. Spinel twinning is possible forming flattened crystals. Also massive and granular.
Cleavage:
perfect in four direction forming cubes.
Fracture:
 uneven and rarely seen because of the perfect cleavage
Hardness:
 2.5+
Specific Gravity:
 approximately 7.5+ (heavy even for metallic minerals)
Streak
 lead gray
Other Characteristics:
 brighter metallic luster on cleavage surfaces than on crystal faces.
Associated Minerals:
 calcite, dolomite, sphalerite, pyrite and other sulfide minerals, also lead oxidation minerals such as cerussite and anglesite.
Local Occurance:
 Davis Quarry
Best Field Indicators:
 crystal habit, cleavage and, perhaps most importantly, density.

Description:

Galena is a common and popular mineral for rock hounds. Its characteristic cubes, distinctive cleavage and high density make it easy to identify and a favorite in high school geology labs. The structure of Galena is identical to that of halite, NaCl. The two minerals have the same crystal shapes, symmetry and cleavage. Some Galena may contain up to 1% silver in place of lead. The large volume of Galena that is processed for lead produces enough Silver as a by product to make Galena the leading ore of Silver.