Eduqas A-level Geology · F1

Elements, minerals and rocks

50 exam-style questions with answers for F1 Elements, minerals and rocks in Eduqas A-level Geology (spec A480QS). Practise with flashcards, a topic quiz, a random quiz across the course, 5 crosswords, or read every question and answer below. Not official Eduqas material.

All 50 questions and answers

Question 1 · Spec F1, Key Idea 1 · Goldschmidt classification
Describe the four groups of the Goldschmidt classification. [2 marks]
Answer:
Lithophile elements associate with silicates and oxides, and siderophile elements with metallic iron (1); chalcophile elements associate with sulfides, and atmophile elements with volatile phases (gases) (1).
Question 2 · Spec F1, Key Idea 1 · Goldschmidt classification
Explain why silicon is concentrated in the silicate Earth rather than the core. [2 marks]
Answer:
Silicon has a strong affinity for oxygen (1); so it forms silicate minerals in the crust and mantle, making it lithophile (1).
Question 3 · Spec F1, Key Idea 1 · Goldschmidt classification
Explain why siderophile elements are concentrated in the Earth's core. [2 marks]
Answer:
During differentiation they entered the dense metallic iron phase (1); which separated and sank towards the centre of the Earth (1).
Question 4 · Spec F1, Key Idea 1 · Goldschmidt classification
Explain why copper and lead are commonly found in sulfide ore minerals. [2 marks]
Answer:
They are chalcophile elements with an affinity for sulfur (1); so they become concentrated in sulfide minerals such as chalcopyrite and galena (1).
Question 5 · Spec F1, Key Idea 1 · Chondrites
Explain why chondrites are used to estimate the Earth's bulk composition. [2 marks]
Answer:
They are undifferentiated meteorites that preserve primitive Solar System material (1); so they represent the material the Earth formed from, not just its differentiated crust (1).
Question 6 · Spec F1, Key Idea 1 · Crustal elements
Name the eight most abundant elements in the Earth's crust. [2 marks]
Answer:
Oxygen, silicon, aluminium and iron (1); calcium, sodium, potassium and magnesium (1).
Question 7 · Spec F1, Key Idea 1 · Silicates
Explain why silicates are the commonest rock-forming minerals. [2 marks]
Answer:
Oxygen and silicon are the two most abundant elements in the crust (1); silicon-oxygen tetrahedra combine with other common elements to form many minerals (1).
Question 8 · Spec F1, Key Idea 1 · Silicates
Describe the structure of a silicon-oxygen tetrahedron. [2 marks]
Answer:
One silicon atom (1); surrounded by four oxygen atoms at the corners of a tetrahedron (1).
Question 9 · Spec F1, Key Idea 1 · Silicate structures
State how isolated, chain, sheet and framework silicates differ. [2 marks]
Answer:
They differ in the number of oxygen atoms shared between neighbouring tetrahedra (1); from none in isolated silicates to all four in framework silicates, giving 1D, 2D or 3D linkages (1).
Question 10 · Spec F1, Key Idea 1 · Silicate structures
Explain why mica has one perfect cleavage. [2 marks]
Answer:
Mica is a sheet silicate with strong bonds within the sheets (1); and weak bonds between the sheets, so it splits easily parallel to them (1).
Question 11 · Spec F1, Key Idea 1 · Silicate structures
Compare oxygen sharing in quartz and in an isolated silicate such as olivine. [2 marks]
Answer:
Quartz is a framework silicate in which all four oxygens of each tetrahedron are shared (1); in isolated silicates no oxygens are shared between tetrahedra (1).
Question 12 · Spec F1, Key Idea 1 · Minerals
Define the term 'mineral'. [3 marks]
Answer:
A naturally occurring inorganic substance (1); with an ordered atomic structure (1); and a characteristic chemical composition expressed by a formula (1).
Question 13 · Spec F1, Key Idea 1 · Rocks
Explain why granite is classed as a rock and not a mineral. [2 marks]
Answer:
It is an aggregate of several minerals, such as quartz, feldspar and mica (1); so it has no single chemical composition or atomic structure (1).
Question 14 · Spec F1, Key Idea 1 · Crystal shape
Distinguish between euhedral, subhedral and anhedral crystals. [3 marks]
Answer:
Euhedral crystals have well-formed crystal faces (1); subhedral crystals have some faces (1); anhedral crystals have no crystal faces (1).
Question 15 · Spec F1, Key Idea 1 · Fracture
Describe conchoidal fracture and name a mineral that shows it. [2 marks]
Answer:
Curved, shell-like breakage surfaces rather than flat cleavage planes (1); shown by quartz (1).
Question 16 · Spec F1, Key Idea 1 · SP1 Hardness
Describe how to compare the hardness of two minerals using a scratch test. [2 marks]
Answer:
Try to scratch a fresh surface of one mineral with the other (1); wipe away the powder to check a permanent groove has formed, not just a mark (1).
Question 17 · Spec F1, Key Idea 1 · SP1 Hardness
A mineral scratches glass but is scratched by quartz. State what this shows about its hardness. [2 marks]
Answer:
It is harder than glass (about 5.5) (1); and softer than quartz (7) (1).
Question 18 · Spec F1, Key Idea 1 · SP1 Streak
Explain why streak is more reliable than colour for identifying ore minerals. [2 marks]
Answer:
Streak shows the colour of the powdered mineral, which is constant (1); surface colour can vary with impurities, weathering or tarnish (1).
Question 19 · Spec F1, Key Idea 1 · SP1 Lustre
Distinguish between metallic and vitreous lustre. [2 marks]
Answer:
Metallic lustre reflects light like a metal, as in galena (1); vitreous lustre looks like glass, as in quartz (1).
Question 20 · Spec F1, Key Idea 1 · SP3 Identification
A mineral has hardness 7, vitreous lustre and no cleavage. Identify it and give one other property that supports your answer. [2 marks]
Answer:
Quartz (1); conchoidal fracture or hexagonal prismatic crystals (1).
Question 21 · Spec F1, Key Idea 1 · SP3 Identification
A mineral has rhombohedral cleavage and effervesces in cold dilute HCl. Identify it and state its hardness. [2 marks]
Answer:
Calcite (1); hardness 3 (1).
Question 22 · Spec F1, Key Idea 1 · SP3 Identification
State how plagioclase can be distinguished from orthoclase in hand specimen. [2 marks]
Answer:
Plagioclase shows repeated (multiple) twinning, seen as fine parallel striations (1); orthoclase shows simple twinning and is often pink (1).
Question 23 · Spec F1, Key Idea 1 · SP3 Identification
State how biotite and muscovite can be distinguished. [2 marks]
Answer:
Both have one perfect basal cleavage (1); muscovite is pale or colourless while biotite is dark brown or black (1).
Question 24 · Spec F1, Key Idea 1 · SP3 Identification
A dark mineral has two cleavages at about 60° and 120°. Identify it, giving a reason. [2 marks]
Answer:
Hornblende (1); because augite has two cleavages at about 90° (1).
Question 25 · Spec F1, Key Idea 1 · SP3 Identification
An olive-green mineral has no cleavage and conchoidal fracture. Identify it and name a rock type it is found in. [2 marks]
Answer:
Olivine (1); found in mafic or ultramafic rocks such as basalt, gabbro or peridotite (1).
Question 26 · Spec F1, Key Idea 1 · SP3 Identification
A hard, red-brown mineral has no cleavage and forms many-faced equant crystals. Identify it. [1 mark]
Answer:
Garnet.
Question 27 · Spec F1, Key Idea 1 · SP3 Identification
Name the mineral that shows a dark cross in square cross-sections and explain the cross. [2 marks]
Answer:
Chiastolite, a variety of andalusite (1); the cross is formed by carbon inclusions arranged in the crystal (1).
Question 28 · Spec F1, Key Idea 1 · SP3 Identification
A mineral has hardness 4, four cleavage directions and often forms cubes. Identify it. [1 mark]
Answer:
Fluorite.
Question 29 · Spec F1, Key Idea 1 · SP3 Identification
A colourless mineral has cubic cleavage, hardness 2.5 and tastes salty. Identify it. [1 mark]
Answer:
Halite.
Question 30 · Spec F1, Key Idea 1 · SP3 Identification
A pale mineral can be scratched by a fingernail and has one good cleavage. Identify it. [1 mark]
Answer:
Gypsum (hardness 2).
Question 31 · Spec F1, Key Idea 1 · SP2 Density
Explain why density is a useful test for barite. [2 marks]
Answer:
Barite is unusually dense for a pale non-metallic mineral, about 4.5 g/cm³ (1); this distinguishes it from similar-looking minerals such as calcite (2.7 g/cm³) (1).
Question 32 · Spec F1, Key Idea 1 · SP3 Identification
A lead-grey metallic mineral has cubic cleavage and a very high density. Identify it and state its approximate density. [2 marks]
Answer:
Galena (1); about 7.5 g/cm³ (1).
Question 33 · Spec F1, Key Idea 1 · SP3 Identification
A brass-yellow metallic mineral forms cubes and scratches glass. Identify it and state its streak. [2 marks]
Answer:
Pyrite (1); greenish-black streak (1).
Question 34 · Spec F1, Key Idea 1 · SP3 Identification
Explain how hardness can distinguish chalcopyrite from pyrite. [2 marks]
Answer:
Chalcopyrite is softer, about hardness 4, so it does not scratch glass (1); pyrite is about hardness 6 and scratches glass (1).
Question 35 · Spec F1, Key Idea 1 · SP3 Identification
A steel-grey mineral leaves a cherry-red streak. Identify it. [1 mark]
Answer:
Haematite.
Question 36 · Spec F1, Key Idea 1 · SP3 Identification
Explain why at least two diagnostic properties should be used to identify a mineral. [2 marks]
Answer:
Many minerals share colour or lustre (1); combining properties such as hardness, cleavage and streak makes the identification more secure (1).
Question 37 · Spec F1, Key Idea 1 · SP1 Acid test
Describe how to carry out the acid test on a mineral and record the result. [2 marks]
Answer:
Add a drop of cold dilute (0.5 mol dm⁻³) hydrochloric acid to a fresh surface (1); record whether there is effervescence or no reaction (1).
Question 38 · Spec F1, Key Idea 1 · SP2 Density
A mineral has a mass of 135 g and a volume of 30 cm³. Calculate its density. [2 marks]
Answer:
Density = mass ÷ volume = 135 ÷ 30 (1); = 4.5 g/cm³ (1).
Question 39 · Spec F1, Key Idea 1 · SP2 Density
Describe how to measure the volume of an irregular mineral specimen. [2 marks]
Answer:
Record the water level in a measuring cylinder, then fully immerse the specimen (1); the volume is the final reading minus the initial reading (1).
Question 40 · Spec F1, Key Idea 1 · SP2 Density
Explain why a larger specimen gives a more accurate density by displacement. [2 marks]
Answer:
A larger volume of water is displaced (1); so the reading uncertainty is a smaller percentage of the measurement (1).
Question 41 · Spec F1, Key Idea 1 · SP2 Density
Density readings are 2.6, 2.7 and 2.8 g/cm³. Calculate the mean. [1 mark]
Answer:
(2.6 + 2.7 + 2.8) ÷ 3 = 2.7 g/cm³.
Question 42 · Spec F1, Key Idea 1 · SP3 Identification
Explain why identification keys should use observable properties. [2 marks]
Answer:
Observable properties can be tested directly on the unknown specimen (1); assuming the rock's origin first could lead to circular reasoning and a wrong identification (1).
Question 43 · Spec F1, Key Idea 1 · Rock textures
Distinguish between crystalline and clastic textures. [2 marks]
Answer:
Crystalline rocks have interlocking crystals (1); clastic rocks have separate grains held together by cement or matrix (1).
Question 44 · Spec F1, Key Idea 1 · Rock textures
Define the term 'well-sorted'. [1 mark]
Answer:
Most grains in the rock are of a similar size.
Question 45 · Spec F1, Key Idea 1 · Rock textures
Explain why aligned platy minerals are evidence of metamorphism. [2 marks]
Answer:
Platy minerals recrystallise perpendicular to directed stress during metamorphism (1); producing a foliation such as slaty cleavage or schistosity (1).
Question 46 · Spec F1, Key Idea 1 · SP4 Drawings
State three features of a good scientific drawing of a rock specimen. [3 marks]
Answer:
Any three from: clear accurate outlines with no shading (1); accurately represents textures and mineral relationships (1); labels and annotations (1); a scale or magnification (1).
Question 47 · Spec F1, Key Idea 1 · SP4 Magnification
A grain 0.8 mm wide measures 16 mm in a drawing. Calculate the magnification. [2 marks]
Answer:
Magnification = image size ÷ actual size = 16 ÷ 0.8 (1); = ×20 (1).
Question 48 · Spec F1, Key Idea 1 · SP4 Magnification
A crystal is 30 mm long in a drawing at ×15 magnification. Calculate its actual length. [2 marks]
Answer:
Actual size = image size ÷ magnification = 30 ÷ 15 (1); = 2 mm (1).
Question 49 · Spec F1, Key Idea 1 · Observations
Distinguish between an observation and an interpretation in a rock description. Give an example of each. [2 marks]
Answer:
An observation is what can be seen, e.g. 'interlocking crystals 4 mm across' (1); an interpretation is inferred from it, e.g. 'slow cooling of magma' (1).
Question 50 · Spec F1, Key Idea 1 · SP3 Identification
State two things a geologist should do if a weathered specimen gives conflicting results. [2 marks]
Answer:
Any two from: test a fresh surface (1); repeat the tests (1); compare several properties with the data sheet (1); record the uncertainty (1).

F2 Surface and internal processes of the rock cycle →

Elements, minerals and rocks

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