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Vaibhav Singh posted an Question
August 13, 2021 • 09:23 am 30 points
  • IIT JAM
  • Geology (GG)

3. the silica deficient mineral is: a.olivine b. feldspar c. feldspathoid d. amphibole (bhu-2013)

3. The silica deficient mineral is: B. Feldspar A. Olivine C. Feldspathoid D. Amphibole (BHU-2013) Answer should be Olivine na??b/c olivine crystallizes earliest from magma and feldspars,quartz ,feldspathoids crystallize last .Also It is known that Silica content increases going down the Bowens rxn series. hence olivine should be silica poor and others are relatively silica rich ,,as usual as I have been taught. BUT ANSWER IS FELDSPATHOID..??HOW

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    Mayank vedwal Vedwal best-answer

    Yes . I also think that answer should be olivine because thee silica contain in olivine is less than feldspathoid that's why we say olivine containing as ultrabasic rock and feldspathoid containing rock as basic rock.

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