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)
1cm
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
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
2cm
Whitish, straw or
silvery in colour
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
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
1cm
Crystals have dark
inclusions in the centre,
like lead in a pencil
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
1cm
Chlorite, Val Di Vizze, Italy
Alteration product
from amphiboles,
pyroxenes and micas
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
1cm
Commonly purple, green
or yellow in colour
Halite or Rock Salt (halide)
Hardness 2.0-2.5,
scratched by a
fingernail
2cm
Perfect cubic
cleavage, 3 planes
intersecting at 90°
Tastes salty when
put on the tongue
Halite, Neuhof, Germany
Gypsum (sulphate)
Hardness 1.5 -2.0, easily
scratched by a fingernail
Perfect basal
(parallel) cleavage
2cm
Often fibrous in
appearance (satin spar)
Arrow head/fish tail
twinned crystals common
Barytes/Barite (sulphate)
Hardness 3.0-3.5,
barely scratched by a
copper coin
Dense for a nonmetallic 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
1cm
Tarnishes to
peacock colours
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)
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
Identify this mineral 1
90°
1cm
Just 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
Cubic crystals with
edges truncated at 45°
2cm
Scratched by steel but not by a copper coin
Identify this mineral 5
2cm
Not scratched by steel, crystal has 12 faces
Identify this mineral 6
2cm
Cleavage
traces
90°
Barely scratched by steel, crystals often show simple twins
Identify this mineral 7
2cm
Feels dense, barely scratched by a copper coin
Identify this mineral 8
Cleavage
directions
1cm
1cm
Just scratched by fingernail
Identify this mineral 9
60°
120°
Cleavage traces
2cm
Just scratched by steel
Identify this mineral 10
2cm
Not scratched by steel
Identify this mineral 11
Cleavage
traces
90°
2cm
Barely scratched by steel, crystals often show multiple twins
Identify this mineral 12
Cleavage
traces
2cm
Scratched by a copper coin
Identify this mineral 13
2cm
Barely scratched by steel, cherry red streak
Identify this mineral 14
1cm
Can be just scratched by a fingernail
Identify this mineral 15
5mm
Not scratched by steel, needle-like crystals
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
Name this mineral 18
1cm
Very dense, scratched by a copper coin, grey streak
Name this mineral 19
1cm
Reacts with acid, barely scratched
by a copper coin, 3 cleavages
Name this mineral 20
Cleavage
traces
1cm
Scratched easily by a fingernail, one plane of cleavage
Name this mineral - Answers
1. Augite
11. Plagioclase
2. Iron Pyrite
12. Biotite
3. Olivine
13. Haematite
4. Fluorite
14. Muscovite
5. Garnet
15. Chiastolite
6. Orthoclase
16. Chlorite
7. Barytes
17. Chalcopyrite
8. Halite
18. Galena
9. Hornblende
19. Calcite
10.Quartz
20. Gypsum