Rocks and minerals: Minerals 2.1.1
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|(a)||minerals as naturally occurring,elements and inorganic compounds whose composition can be expressed as a chemical formula||To include:native sulphur and copper, calcite and quartz
Learners should be able to recognise the mineral in a chemical formula but not recall the specific formula of individual minerals
|b)||rock-forming silicate minerals as crystalline materials built up from silicon-oxygen tetrahedra to form frameworks, sheets or chains and which may have a range of compositions (qualitative only)||To include:
|c)||i) the diagnostic physical properties of the major rock-forming minerals in hand specimens
(ii) the classification of samples, photographs and thin section diagrams of minerals using their diagnostic physical properties
(iii) practical investigations to determine the density and hardness of rock samples
|To include: colour, lustre, shape, streak, cleavage/fracture, density, hardness
|d)||rocks as mixtures of one or more minerals that are classified as igneous, sedimentary and metamorphic using their relationship to temperatures and pressures in the rock cycle|
An observation based exercise to introduce colour, lustre, shape and cleavage.
Cleavage is often harder to see – thin section on the web may be easier.
A follow-on for ‘Be a mineral expert 1’, with streak, density, hardness, acid test.
The density test is quite simple – the samples need to be a similar size.
A website using a virtual microscope. Thin sections of different rocks can be viewed. It also goes through six physical characteristics of minerals.
The virtual microscope is good for looking at cleavage in some minerals (pyroxene in particular).
Dichotomous key for identifying the most common silicate and carbonate minerals in rock samples, outcrops and in building stones, using a basic tool kit (hand lens, steel nail and a piece of copper).
Acid test for calcite and dolomite is mentioned but is not required.
In this the first topic of the course learners are introduced to the basic geological toolkit needed to identify minerals, rocks and their properties and to start to understand the science behind their composition. The topic includes defining minerals with significant links to key stage 3 science definitions of elements and compounds. Following this learners consider the atom by atom 3-dimensional structure of the silicate minerals and the variety of arrangements which can occur. Learners then consider the physical skills that geologists use to identify minerals by using hand specimens of rocks and minerals, photographs and thin sections. Finally, learners start to build combinations of minerals into different rock types and consider the settings where they form.
Common misconceptions or difficulties students may have:
The main challenges within this topic are likely to include learners struggling with understanding chemical formula and how elements fit into the silicate structure. This may be due to learners lacking confidence in this area at GCSE level and these concerns carrying through. To help learners remember that they don’t need to recall the chemical formula of other minerals only those listed, focus on patterns and how the periodic table can be a useful tool.
Conceptual links to other areas of the specification – useful ways to approach this topic to set students up for topics later in the course:
The basic geological skills introduced in this section are revisited throughout the geology course and in further studies in this subject and other scientific subjects, in particular it relates to module 3 Global tectonics and module 5 petrology and economic geology.
To begin the topic learners could be introduced to what a mineral is with its associated definition, to relate this to previous studies learners could consider how elements, compounds and mixtures are defined. Learners could be given a range of examples to consider. Following this learners could be introduced to silicate structures by using the link to silicate structures construction, this could be an activity carried out over several lessons, it could be started in groups which could come together to build larger structures. A worksheet is provided on the site for learners to record observations, learners should consider how the structures build up in terms of ratios and in range of composition.
Learners could then use mineral hand specimens where available together with the mineral guide linked below to experience how geologists observe and investigate mineral properties. To help apply their experience of minerals to the rock cycle learners could investigate the interactive rock cycle below and consider igneous, sedimentary and metamorphic settings.
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