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Its name, given by Weed and Pirsson in 1895, is derived from Shonkin, the Indian name for the Highwood Mountains of Montana.
A coarse-grained rock with abundant augite, some olivine, biotite or hornblende, and essential alkali feldspar and foids, usually nepheline. Now defined modally as a melanocratic variety of foid syenite in QAPF field 11. A dark-colored syenite composed chiefly of augite and alkali feldspar, and possibly containing olivine, hornblende, biotite, and nepheline.
Classification of ShonkiniteHide
Sub-divisions of ShonkiniteHide
Mineralogy of ShonkiniteHide
Essential minerals - these are minerals that are required within the classification of this rock:
|Feldspar > Alkali Feldspar||Feldspar Group minerals rich in Potassium or Sodium.|
|Feldspathoid||A family of rock-forming minerals consisting of aluminosilicates of sodium, potassium, or calcium and having too ...|
Non-essential minerals - these minerals are common, sometimes major components, but are not always present: