Neco 2025 Geography Question 16
Practice objective / multiple choice question 16 from the 2025 Neco Geography examination.
A rock sample has the following mineral composition by weight: quartz 30%, K-feldspar 25%, plagioclase 20%, biotite 15% and amphibole 10%. Assume the silica (SiO2) content of each mineral is: quartz 100%, K-feldspar 65%, plagioclase 55%, biotite 45% and amphibole 45%. Compute the overall silica percentage of the rock and state whether the rock is classified as felsic (silica > 65%) or mafic (silica ≤ 65%).
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About This Question
This is Neco 2025 Geography Question 16. It is one of the objective questions from the 2025 Neco Geography examination.
Difficulty level: Medium .
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