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Back to Basics - Physical Properties of Minerals: Tenacity

Posted by Maryanne Fender on

Back to Basics - Physical properties of Minerals

Identifying minerals starts by observing basic physical properties in hand.  Briefly the physical properties are 
  1. Strength or Tenacity
  2. Fracture, Cleavage and Partings
  3. Hardness
  4. Heat, Melting points, conductivity
  5. Magnetism
  6. Radioactivity
  7. Color
  8. Streak
  9. Crystalline Structure
  10. Diaphaneity or Amount of Transparency 
  11. Luster
  12. Odor
  13. Taste
  14. Specific Gravity

When the strength properties of of species within mineral classes are compared it becomes apparent why minerals were classified by chemical-structural criteria.

Tenacity: Definition
Tenacity is the resistance that a mineral offers to breaking, crushing, bending, cutting, or other acts of destruction. Fracture is how the mineral breaks once the tenacious limit has been exceeded.

Minerals in the classes, in general, share similar characteristics as outlined:
Native Metals: Soft, malleable, sectile  (gold)
Semi-Metals: Soft, somewhat sectile, brittle (bismuth)
Native Elements: Sulfur - soft and brittle, Diamond - hard and brittle, Graphite - soft and sectile
Sulfides and Sulfosalts: Generally soft and brittle though the pyrite group is considerably harder (stibnite)
Oxides: Hard to very hard, brittle  with the notable exceptions of cuprite and zincite (chrysoberyl)
Hydroxides: Vary from soft to hard, brittle (brucite)
Halides: Soft, brittle, Outstanding cleavages (salt)
Borates: Soft, brittle, outstanding cleavages (colemanite)
Sulfates: Soft, brittle, outstanding cleavages (gypsum)
Molybdates: Soft, brittle, cleavages poor (molybdenum)
Phosphates: Soft to moderately hard, brittle, cleavage common (ludlamite)
Silicates: Variation in hardness but on average very hard, brittle (quartz)

Reference:  Mineralogy, John Sinkankas