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EnglandGeologyQuick questions
Module 2: Foundations in geology - Minerals and rocks
Quick questions on Rock-forming minerals and silicate structures: the silica tetrahedron, silicate groups and mineral identification - OCR A-Level Geology
6short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.
What is the silica tetrahedron?Show answer
Almost all the minerals that make up the crust are silicates, built from a single repeating unit: the silica (or silicon-oxygen) tetrahedron. One small silicon atom sits at the centre, bonded to four oxygen atoms at the corners, giving the unit a charge of .
What are the silicate groups?Show answer
The groups are defined by how many of the four corner oxygens each tetrahedron shares with its neighbours. Sharing more oxygens (more polymerisation) means a higher proportion of silicon and oxygen and a more rigid structure.
What is physical properties for identification?Show answer
You identify minerals in hand specimen using a fixed set of properties:
What is q1?Show answer
State the formula of the silica tetrahedron and name the group of silicates in which every tetrahedron shares all four oxygens. [2 marks]
What is q2?Show answer
Explain why mica has a perfect cleavage in one direction. [2 marks]
What is q3?Show answer
Give two physical properties that distinguish quartz from feldspar in hand specimen. [2 marks]
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