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.
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)
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
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
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
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.
Notes de l'éditeur
Ionic radius is the distance from the nucleus of an ion up to which it has an influence on its electron cloud.
Common rocks include granite, basalt, limestone, and sandstone.
Luster is how the surface of a mineral reflects light. It is not the same thing as color, so it is crucial to distinguish luster from color. For example, a mineral described as “shiny yellow” is being described in terms of luster (“shiny”) and color (“yellow”), which are two different physical properties.
Streak is the color of a powdered mineral, produced by grinding a corner of a mineral specimen across a porcelain tablet called a streak plate. Streak is more consistent than the color of a whole mineral. (Minerals with a hardness greater than the streak plate have no streak.)
hen a mineral breaks irregularly, the breaks are called fractures. The breaks can be described as grainy, hackly (jagged), conchoidal (curved), or splintery.
A crystal is defined as a homogenous solid possessing a three-dimensional internal order defined by the lattice structure
the ratio of the density of a substance to the density of a standard, usually water for a liquid or solid, and air for a gas.
To determine the specific gravity of our sample, we simply divide the mass of the sample (that is, 150 grams) by the mass of the same volume of water, which would be 20 grams. So, specific gravity = 150 grams of the sample / 20 grams of water.
This also means that specific gravity does not have any units. One of the reasons why specific gravity is a unitless quantity is that it is the ratio of two quantities with same dimensions or units. Specific gravity is simply the ratio of two densities of two objects or substances.
Silicon dioxide
glass for drinking, glass for protection, fiberglass for insulation, the floor tiles and shower basins in our bathrooms, and the tableware from which we eat
hey are heat tolerant, insulating and dielectric. Because of these properties, they are used in electrical appliances. They are used in control devices, heating devices, neon lights and other lighting equipment.
Amphibolite is a common dimension stone used in construction, paving, facing of buildings, especially because of its attractive textures, dark color, hardness and polishability and its ready availability.
Pyroxene is the name of a group of dark-colored rock-forming minerals found in igneous and metamorphic rocks throughout the world. They form under conditions of high temperature and/or high pressure.
A few pyroxene minerals are used as gem materials, but only in rare instances when they have attractive color and clarity. Jadeite, diopside, and spodumene are the most important pyroxene gem materials.
In crystal healing, Peridot and Olivine are often used as "anti-anger stones" when everyday life is characterized by negative aspects. The fresh green color of Peridot has the effect of a stroll outside during the blissful month of May.
Calcite crystal's properties make it one of the most widely used minerals. It is used as abuilding material, abrasive, agricultural soil treatment, construction aggregate, pigment, pharmaceutical, and other applications. It has more applications than nearly any other mineral.
