WJEC AS Mineral Guide I.G.Kenyon

Quartz (silicate) Hardness 7, not scratched by steel No cleavage but shows conchoidal fracture Hexagonal crystals terminated by pyramids 5mm 1cm Quartz (variety citrine) Rose quartz showing conchoidal fracture

Orthoclase Feldspar (silicate) Hardness 6, barely scratched by steel 2 cleavages intersecting at 90° results in blocky shape Commonly flesh coloured Crystals show simple twinning 2cm

Plagioclase Feldspar (silicate) Hardness 6, barely scratched by steel 2 sets of cleavages intersecting at 90° resulting in blocky form Commonly creamy white or grey in colour Crystals show multiple or repeated twins 1cm

Biotite Mica (silicate) Hardness 2.5-3.0 scratched by a copper coin Shows perfect basal (parallel) cleavage Has a distinct pearly lustre Brown or black in colour 2cm

Muscovite Mica (silicate) Hardness 2.5-3.0 scratched by a copper coin Shows perfect basal (parallel) cleavage Has a distinct pearly lustre Whitish, straw or silvery in colour 2cm

Hornblende (amphibole/silicate) Hardness 5.0-6.0, just scratched by steel 2 sets of cleavages intersecting at 60°/120° Greenish black in colour 1cm

Augite (pyroxene/silicate) Hardness 5.0-6.0, just scratched by steel 2 sets of cleavages intersecting at 90° Greenish black in colour

Hardness 6.0-7.0, not scratched by steel Olivine, Canary Islands Olivine (silicate) Hardness 6.0-7.0, not scratched by steel Olive green in colour No cleavage 2cm Olivine, Canary Islands

Andalusite/Chiastolite (silicate) Hardness 6.5-7.5, not scratched by steel Occurs as needle-like crystals but square in cross-section Crystals have dark inclusions in the centre, like lead in a pencil 1cm

Garnet (silicate) Hardness 6.5-7.5, not scratched by steel Rhombdodecahedral crystal form, 12 faces each one a rhombus No cleavage Red/brown or green in colour 2cm Almandine Garnet, Peru

Chlorite (silicate) Hardness 2.0, scratched by fingernail Perfect basal (parallel) cleavage Greenish colour Feels greasy when rubbed between the fingers Alteration product from amphiboles, pyroxenes and micas 1cm Chlorite, Val Di Vizze, Italy

Hardness 3, just scratched by a copper coin Calcite (carbonate) Hardness 3, just scratched by a copper coin Perfect rhombohedral cleavage, 3 planes intersect at 60°/120° to give cleavage rhombs Effervesces and gives off carbon dioxide when dilute hydrochloric acid is applied 1cm

Fluorite (halide) Hardness 4, scratched easily by steel but not by a copper coin Perfect octahedral cleavage, cubic crystals have the corners missing at a 45° angle Fluoresces in ultra violet light Commonly purple, green or yellow in colour 1cm

Halite or Rock Salt (halide) Hardness 2.0-2.5, scratched by a fingernail Perfect cubic cleavage, 3 planes intersecting at 90° Tastes salty when put on the tongue 2cm Halite, Neuhof, Germany

Gypsum (sulphate) Hardness 1.5 -2.0, easily scratched by a fingernail Perfect basal (parallel) cleavage Often fibrous in appearance (satin spar) Arrow head/fish tail twinned crystals common 2cm

Barytes/Barite (sulphate) Hardness 3.0-3.5, barely scratched by a copper coin Dense for a non-metallic mineral (4.5) Often shows perfect basal (parallel) cleavage, occasionally displays 2 cleavages Commonly shows bladed crystal 2cm

Chalcopyrite (sulphide) Hardness 4, not scratched by a copper coin Black streak with gold strands within it Metallic lustre Greenish gold colour Tarnishes to peacock colours 1cm

Iron Pyrite/Pyrite (sulphide) Greenish black streak Hardness 6.0, barely scratched with steel Metallic lustre Brassy gold colour Cubic crystals show striated faces Strikes fire (sparks) with steel 1cm

Galena (sulphide) Perfect cubic cleavage, 3 planes intersect at 90° 1cm Perfect cubic cleavage, 3 planes intersect at 90° Hardness 2.5, easily scratched by a copper coin Lead grey streak Very dense (7.5)

Haematite (oxide) Hardness 5.5-6.5, barely scratched by steel Cherry red streak Metallic lustre Often occurs as kidney shaped masses with a fibrous internal structure 1cm

Just scratched by steel Identify this mineral 1 90° 1cm Just scratched by steel

Greenish black streak, barely scratched by steel Identify this mineral 2 1cm Greenish black streak, barely scratched by steel

Identify this mineral 3 2cm Not scratched by steel, no cleavage

Identify this mineral 4 Scratched by steel but not by a copper coin Cubic crystals with edges truncated at 45° 2cm Scratched by steel but not by a copper coin

Not scratched by steel, crystal has 12 faces Identify this mineral 5 2cm Not scratched by steel, crystal has 12 faces

Barely scratched by steel, crystals often show simple twins Identify this mineral 6 2cm Cleavage traces 90° Barely scratched by steel, crystals often show simple twins

Feels dense, barely scratched by a copper coin Identify this mineral 7 2cm Feels dense, barely scratched by a copper coin

Just scratched by fingernail Identify this mineral 8 Cleavage directions 1cm 1cm Just scratched by fingernail

Just scratched by steel Identify this mineral 9 60° 120° Cleavage traces 2cm Just scratched by steel

Identify this mineral 10 2cm Not scratched by steel

Barely scratched by steel, crystals often show multiple twins Identify this mineral 11 Cleavage traces 90° 2cm Barely scratched by steel, crystals often show multiple twins

Scratched by a copper coin Identify this mineral 12 Cleavage traces 2cm Scratched by a copper coin

Barely scratched by steel, cherry red streak Identify this mineral 13 2cm Barely scratched by steel, cherry red streak

Can be just scratched by a fingernail Identify this mineral 14 1cm Can be just scratched by a fingernail

Not scratched by steel, needle-like crystals Identify this mineral 15 5mm Not scratched by steel, needle-like crystals

Scratched by a fingernail, fibrous/flaky, feels greasy Identify this mineral 16 1cm Scratched by a fingernail, fibrous/flaky, feels greasy

Name this mineral 17 2cm Scratched easily by steel but not by a copper coin, black streak with gold strands

Very dense, scratched by a copper coin, grey streak Name this mineral 18 1cm Very dense, scratched by a copper coin, grey streak

Reacts with acid, barely scratched by a copper coin, 3 cleavages Name this mineral 19 1cm Reacts with acid, barely scratched by a copper coin, 3 cleavages

Scratched easily by a fingernail, one plane of cleavage Name this mineral 20 Cleavage traces 1cm Scratched easily by a fingernail, one plane of cleavage

Name this mineral - Answers Augite Iron Pyrite Olivine Fluorite Garnet Orthoclase Barytes Halite Hornblende Quartz 11. Plagioclase 12. Biotite 13. Haematite 14. Muscovite 15. Chiastolite 16. Chlorite 17. Chalcopyrite 18. Galena 19. Calcite 20. Gypsum