This document provides information about common rock-forming minerals. It discusses the composition, properties and occurrence of silicate minerals like quartz, feldspar, mica, amphibole and pyroxene. It also covers the carbonate mineral calcite and the silicate mineral olivine. These minerals are important components of igneous, metamorphic and sedimentary rocks.

1. MODULE 3: ROCKS
AND MINERALS

2. Learning competency

3. EARTH'S INTERNAL
STRUCTURE

5. • Naturally-occurring
• Inorganic
• Solid
• Definite Chemical Composition
• Ordered Internal Structure
MINERAL

6. • Silicates
• Oxides
• Sulfides
• Sulfates
• Halides
• Carbonates
• Native Metals
Composition of Minerals
Minerals can be classified into several classes which are mainly composed of elements that
ara abundant on Earth's crust
Quarts (SiO2)
Hematite (Fe2O3)
Pyrite (FeS2)
Gypsum (CaSO4 *
2H2O)
Rock Salt (NaCl)
Calcite (CaCO3) Gold (Au)

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8. •
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9. Mineralogist - scientist who study minerals
Mineralogy - study of minerals
Petrology - study of rocks
Edaphology - study of soil in realtion to higher plants
Pedology - study of soil with emphasis on its structure and genesis

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1. LUSTER
Chalcedony
Quartz
Galena
Pyrite

11. 2. COLOR

12. 3. STREAK
- Color of the mineral in its powdered form.
Streak is useful for identifying metallic and
earthy luster, because minerals with
nonmetallic luster generally have a colorless
or white streak that is not diagnostic.
Streak is obtained by scratching the
mineral on an unpolished piece of
white porcelain called STREAK
PLATE.
Streak is commonly more reliable than color
for identifications

13. 4. HARDNESS
-resistance of mineral to scratching or
abrasion by other materials.
- Hardness is determined using Moh’s
Hardness Scale - devised (1812) by the German
mineralogist Friedrich Mohs
With Moh’s scale, anyone can test an
unknown mineral for its hardness.
Imagine you have an unknown mineral. You
find that it can scratch fluorite or even
feldspar, but apatite scratches it. You know
that the mineral’s hardness is between 5
and 6.
Note: no other mineral can scratch diamond

14. 5. CLEAVAGE

15. 6. FRACTURE

16. 7. CRYSTAL FORM
- Is a solid, homogenous, orderly array of atoms and may be nearly any size. The arrangement of
atoms within a mineral determines the external shape of its crystals. Some crystals have smooth,
planar faces and regular, geometric shapes; these are what most people think of as crystals
Hexagonal prisms – quartz with
pyramid-like shapes
Cubes or Pyritohedrons – forms with
twelve pentagonal faces. Ex. Pyrite
Dodecahedrons – twelve sided forms
that have a roughly round shape.
Ex. Garnets

17. 8. SPECIFIC
GRAVITY

19. 1. Solubility
2. Melting point
3. Chrystallographic techniques

21. COMMON ROCK-FORMING
MINERALS
• SiO2)
•
KAlSi3O8
NaAlSi3O8
•
H2KAl3(SiO4)3
K(Mg,Fe)3(AlSi3O10)(OH,F)2
• CaAl(AlSi)O6)
• Ca(Mg,Fe,Al)4(AlFeTi)3SiO6)
• NaCa2(Mg,Fe,Al)5(Al,Si)8O22(OH)2
• (Mg, Fe)2SiO4

22. Quartz
Quartz which is usually called silica, is one of the most common minerals in the
Earth's crust.
•Quartz is made up of silicon dioxide (SiO2)
•Quartz crystals are usually hexagonal and prismatic in shape.
•Pure quartz is colourless, although the presence of impurities may give a range of
colours, such as violet, pink and orange.
•Quartz is the raw material for making glass

23. Feldspar
Plagioclase Feldspar
Plagioclase feldspar is a sodium- or calcium-rich feldspar. The chemical
composition ranges from sodium aluminium silicate, NaAlSi3O8 to calcium
aluminium silicate, CaAl2Si2O8.
•Plagioclase feldspar crystals usually occur as stubby prisms.
•Plagioclase feldspar is generally white to grey and has a vitreous lustre.
•Plagioclase feldspar is an important industrial mineral used in ceramics.
Alkali Feldspar
 Alkali feldspar is another member of the family of feldspar minerals.
 Alkali feldspar (Potassium aluminium silicate (K,Na)AlSi3O8) are rich in
alkali metal ions.
 Alkali feldspar crystals usually occur as stubby prisms.
 Alkali feldspar is commonly pink to white.
 Alkali feldspar is used as raw material to make porcelain.

24. Micas
 Micas are a family of silicate minerals.
 Micas are made up of varying amounts of potassium, magnesium, iron,
as well as aluminium, silicon and water.
 Micas form flat, book-like crystals that split into individual sheets,
separating into smooth flakes along the cleavage planes.
 They are common minerals in intrusive igneous rocks, and can also be
found in sedimentary and metamorphic rocks.
 Biotite is a dark, black or brown mica; muscovite is a light-coloured or
clear mica.

25. Amphiboles
Amphiboles are a family of silicate minerals.
•Amphibole minerals generally contain iron, magnesium, calcium and
aluminium as well as silicon, oxygen, and water.
•Amphiboles form prismatic or needle-like crystals.
•Amphibole is a component of many igneous and metamorphic rocks.
•Hornblende is a common member of the amphibole group of rock-
forming minerals.

26. Pyroxene
 Pyroxenes are a family of silicate minerals.
 Pyroxene minerals generally contain magnesium, iron, calcium and
aluminium as well as silicon and oxygen.
 Pyroxenes form short or columnar prismatic crystals.
 Pyroxene is a component in many igneous and metamorphic rocks.
 Pyroxene crystals are commonly faceted as gemstones. For
instance, precious jade (jadeite) is a pyroxene.

27. Olivine
Olivine is a silicate mineral.
•Olivine ((Mg,Fe)2SiO4) contains iron and magnesium.
•Olivine is a green, glassy mineral.
•Olivine is common in mafic and ultramafic rocks, but has not been found
in Hong Kong.
•Clear and transparent olivine crystals are commonly faceted as
gemstones.

28. Calcite
Calcite is a carbonate mineral.
•Calcite is made up of calcium carbonate (CaCO3).
•Calcite is generally white to clear, and is easily scratched with
knife.
•Calcite is a common sedimentary mineral that is the major
component of calcareous sedimentary rocks such as limestone.
Metamorphism of limestone produces marble.