Chapter 2 Rock第二章 岩石

Since minerals are the building blocks of rocks, it is

important that you learn to identify the most common

varieties. Minerals can be distinguished using various

physical and/or chemical characteristics, but, since

chemistry cannot be determined readily in the field, the

physical properties of minerals are used to identify

them.

§2-1: The main minerals in the rock( 造岩矿物 )

♥ Crystal form （晶形）

♥ Hardness （硬度）

(relative to a steel blade or you finger nail),

♥ colour( 真色，假色，它色 )

♥ Luster （光泽）

♥ Streak ( 条痕 )

(the colour when a mineral is ground to a powder).

♥ cleavage （解理）

Physical properties of minerals includefeatures such as ：

Quartz is hard - it can easily scratch a steel knife blade. In many rock

s, quartz grains are irregular in shape because crystal faces are rare

and quartz does not have a cleavage(ie, it does not break on regular

flat faces).

1 Quartz( 石英 ):

Quartz is a glassy looking, transparent or t

ranslucent mineral which varies in colour f

rom white and grey to smoky. When there

are individual crystals they are generally c

lear, while in larger masses quartz looks

more milky white. 油脂光泽

Feldspar is also hard but can be scratched by quartz. Feldspar in ign

eous rocks （火成岩） forms well developed crystals which are roughl

y rectangular in shape, and they cleave or break along flat faces. The

grains, in contrast to quartz, often have straight edges and flat rectang

ular faces, some of which meet at right angles.

2 Feldspar （长石） :

Feldspar is the other common, light-coloured rock-forming m

ineral. Instead of being glassy like quartz, it is generally dull

to opaque （不透明） with a porcelain-like appearance. Col

our varies from red, pink (orthoclase 正长石 ), and white to

green, grey (plagioclase 斜长石 ).

Plagioclase斜长石

Orthoclase正长石

The most common amphibole is h

ornblende （角闪石） . Hornblen

de is quite similar to augite （普通

辉石） in that both are dark mine

rals, however hornblende crystals

are generally longer, thinner and

shinier than augite and the minera

l cross-sections are diamond-sha

ped.

hornblende （角闪石）

3 Amphibole （闪石）

The most common pyroxene mineral

is augite. Augite is generally dark gre

en to black in colour and forms short,

stubby （短而粗） crystals which, if

you look at an end-on section, have s

quare or rectangular cross-sections.

Pyroxene （辉石）

4 Pyroxene 辉石

Talc occurs in granular （粒状的）

or foliated （片状的） masses so

metimes known as soapstone （皂

石） . It is white to green, sometim

es grey or brownish. It is very soft a

nd will be scratched by a finger nail.

It has a greasy feel （滑感）

5 Talc （滑石）

Olivine in the jewellery trade, is ye

llow-green, translucent （半透明的） and glassy looking. Crystals

are not common; it usually occurs

as rounded grains in igneous （火成的） rocks or as granular mass

es. Olivine is almost as hard as qu

artz; it does not have a well-develo

ped cleavage.

6 Olivine 橄榄石

Mica is easily distinguished by i

ts characteristic of peeling into

many thin flat smooth sheets or

flakes （薄片） . This is similar

to the cleavage in feldspar exc

ept that in the case of mica the

cleavage planes are in only on

e direction and no right angle f

ace joins occur. Mica may be w

hite and pearly or dark and shi

ny .

7 Mica 云母

8 Gypsum (plaster stone, 石膏 )

9 Kaolinite ( 高岭石 )

10 Montmorillonite （蒙脱石）

11 Water mica （伊利石）

§2-2: Rock( 岩石 )( 一种或多种矿物组成的集合体 )

一 、 The classification of rock according to the cause of formation

igneous rock （岩浆岩）

(magma rock)

sedimentary rock （沉积岩）

metamophic rock （变质岩）

岩石

二、 Igneous rock

1 the formation of igneous rock: Deep within the Earth, rock is kept in a molten （融熔

的） state due to extreme temperature and pressure. 

This molten rock is called magma （岩浆） .  The mag

ma is constantly moving and sometimes moves its wa

y to the surface through the cracks （裂缝） in the soli

d rock.  Once it reaches the surface, it is called lava

（熔岩） . 

The location it pushes through to the surface is call

ed a volcano （火山） .  The opening in the volcano

that the lava erupts out of is called a vent( 出口 ).  Fo

r many volcanos, there is more than one vent.  Ofte

n volcanos have a funnel （漏斗） shape with a pit

at the top.  This pit is called a volcanic crater （火山

口） .  If this crater becomes very large, the walls of

the crater might collapse to produce a feature called

a caldera （喷火山口）

How Igneous rock rock Is FormedPyroclastic ash( 火山灰 )

Batholith岩基 Captive mass

俘虏体

laccolith岩盘

岩墙Rock wall

岩株

Volcano neck

火山颈

Lava flow岩流

2 the formation state of igneous rock（岩浆岩的产状）

Sill 岩床

3 the classcification of igneous rock （岩浆岩的分类）

（ 1 ） According to the formation state( 按产状 )

◈Intrusive Igneous Rocks （侵入岩） - usually medium to coarse grained texture due to slow cooling. Typically light coloured. ◈ Extrusive Igneous Rocks （喷出岩） - glassy or fine-grained due to rapid cooling. May have voids due to degassing of the magma. Typically dark coloured.

(2) According to the Silica Content and Mineral Composition( 根据二氧化硅含量 )

◈ Acid Igneous Rocks( 酸性岩 ) - silica rich ( > 65% by weight) composed mainly of light coloured minerals (eg. feldspars, quartz)

◈ Intermediate Igneous Rocks （中性岩） - silica 50-65% by weight, composed mainly of feldspars, some mafic （铁镁质的 minerals, with some quartz.

◈ Basic Igneous Rocks （基性岩） - silica poor ( < 50% by weight) contain significant

amounts of mafic or dark coloured ferromagnesian mineral

s (eg. olivines, pyroxenes, amphiboles, micas). No free qua

rtz.

3the description of main igneous rock （岩浆岩描述）

◈ granite （花岗岩）

Granite is an igneous rock that is composed of four

minerals. These minerals are quartz, feldspar, mica, a

nd usually hornblende. Granite forms as magma cools f

ar under the earth's surface. Because it hardens deep u

nderground ， it cools very slowly. This allows crystals

of the four minerals to grow large enough to be easily s

een by the naked eye.

Granite is an excellent material for building bridges and

buildings because it can withstand thousands of pounds of pressure.

It is also used for monuments because it weathers slowly.

Engravings in the granite can be read for hundreds of years, making

the rock more valuable.

Granite is quarried in many places in the world including the

United States. The State of New Hampshire has the nickname

"Granite State" because of the amount of granite in the mountains of

that beautiful state. The Canadian Shield of North America contains

huge outcroppings (surface rocks) of granite.

◈ porphyritic granite ( 花岗斑岩 )

shallow intrusive rock （浅成侵入岩） moderate crystallization （中等结晶） porphyritic structure 斑状结构 quartz-feldspar-black mica

花岗斑岩

◈ rhyolite （流纹岩）

Rhyolite is very closely related to granite. The difference is r

hyolite has much finer crystals. These crystals are so small th

at they can not be seen by the naked eye. Rhyolite is an extru

sive igneous rock having cooled much more rapidly than granit

e, giving it a glassy appearance. The minerals that make up rh

yolite are quartz, feldspar, mica, and hornblende.

Rhyolite流纹岩

◈ Diorite ( 闪长岩 )

1 abyssal intrusive rock2 well crystallization 3 feldspar, quartz, amphibole

◈ Diorite porphyrite （闪长玢岩）

1 shallow intrusive rock,2 median crystallization 3 feldspar, quartz amphibole

Dacite is an extrusive igneous rock. The principle minerals that make up dacite are plagioclase, quartz, pyroxene, or hornblende. Dacite

安山岩

◈ Dacite （安山岩）

Andesite

◈ pyroxenire ( 辉岩 ) 

1 abyssal intrusive rock2 well crystallization 3 amphibole, phyroxene feldspar

Basalts are dark colored, fine-gra

ined extrusive rock. The mineral gra

ins are so fine that they are impossi

ble to distinguish with the naked ey

e or even a magnifying glass （放大镜） . They are the most widesprea

d of all the igneous rocks. Most bas

alts are volcanic in origin and were f

ormed by the rapid cooling and hard

ening of the lava flows. Some basalt

s are intrusive having cooled inside

the Earth's interior.

◈ basalt 玄武岩

1 ultrabasic rock （超基性岩石） (sio2<45%)

2 abyssal intrusive rock （深成岩） 3 well crystallization （结晶好） 4 olivine ； pgroxene

◈ olivine rock( 橄榄岩 )

◈ Obsidian 黑耀岩

Obsidian is a very shiny nat

ural volcanic glass. When o

bsidian breaks it fractures wit

h a distinct conchoidal （贝壳状的） fracture. Notice in

the photo to the left how it fr

actures. Obsidian is produced

when lava cools very quickly.

The lava cools so quickly th

at no crystals can form.

When people make glass they melt silica rocks like sand and quartz then cool it rapidly by placing it in water. Obsidian is produced in nature in a similar way.

Obsidian is usually black or a very dark green, but it can also be found in an almost clear form.

Pumice is a very light colored, frothy （起泡的） volcanic r

ock. Pumice is formed from lava that is full of gas. The lava is e

jected and shot through the air during an eruption. As the lava h

urtles （急飞） through the air it cools and the gases escape le

aving the rock full of holes.

◈ Pumice （浮石）

Pumice is so light that it actually floats on water. Huge

pumice blocks have been seen floating on the ocean after

large eruptions. Some lava blocks are large enough to

carry small animals.

三、 sedimentary rock （沉积岩）

1 the formation of sedimentary rock: For thousands, even millions of years, little pieces of our

earth have been eroded--broken down and worn away by

wind and water. These little bits of our earth are washed

downstream where they settle to the bottom of the rivers,

lakes, and oceans. Layer after layer of eroded earth is

deposited on top of each. These layers are pressed down

more and more through time, until the bottom layers slowly

turn into rock.

How Sedimentary Rock Is Formed

Sediments are subdivided into three types: ▦1 Clastic or detrital sediments （碎屑岩） Comprising particles of various sizes carried in suspension by wind, water or ice. Sand ( 砂岩 )is an example of a clastic sediment. Silt （粉砂岩） and sand size particles are carried in suspension by wind, water and ice.  

2 the classification of sedimentary rock:

  ▦2 Chemical or precipitated sediments （化学岩）

which are carried in aqueous solution. Salt (halite) is a

n example of a chemical precipitate.

▦3 Organic or biogenic sediments （有机岩）

precipitated or accumulated by biological agents. Man

y organisms promote the precipitation of calcite to form b

iogenically precipitated calcareous （含钙的） muds.

3 The texture and structure of sedimentary rock 沉积岩的结构和构造

沉积岩的层理构造

平行层理

斜层理

波状层理

印模

粒序层理

交叉层理

沉积岩的结构特征

砂粒 孔隙 胶结物

砂粒

粘粒粉粒

铁饼形的

Sphericity 球形度[ sfe’risiti ]

4 the description of sedimentary rock

Conglomerate rocks are sedimentary ro

cks. They are made up of large sedimen

ts like sand and pebbles （鹅卵石） . T

he sediment is so large that pressure al

one cannot hold the rock together; it is a

lso cemented together with dissolved mi

nerals.

◈ gravel stone (conglomerate) 砾岩 (clastic rock)

◈ sand stone (d=2-0.05mm) 砂岩

Sandstone rocks are sedimentary rocks

made from small grains of the minerals

quartz and feldspar. They often form in

layers as seen in this picture. They are

often used as building stones.

◈ silt stone(d=0.05-0.005mm) 粉砂岩

◈ mud stone (d<0.005mm) 泥岩

kaolinite( 高岭石 )

montorillonite （蒙脱石）

water mica （伊利石）

Mineral Composition

Shale rock is a type of

sedimentary rock formed

from clay that is

compacted together by

pressure. They are used

to make bricks

◈ shale stone(d<0.005mm) 页岩

Limestone rocks are

sedimentary rocks that are made

from the mineral calcite which came

from the beds of evaporated seas

and lakes and from sea animal

shells. This rock is used in concrete

and is an excellent building stone for

humid regions. color grey

◈ lime stone 石灰岩

◈ dolomite rock 白云岩

color: white-grey

mineral: dolomit

◈ Gypsum 石膏

Gypsum rocks are sedimentary rocks made up of sulfate

mineral and formed as the result of evaporating sea water in

massive prehistoric basins. It is very soft and is used to make

Plaster of Paris, casts, molds, and wallboards.

四、 Metamorphic rock （变质岩）

Metamorphic rocks are generated by recrystalliz

ation of either igneous or sedimentary rocks by th

e action of any or all of the following: Pressure, T

emperature, Pore Fluids.

The type of metamorphic rock is determined by the parent ro

ck （母岩） and the P/T conditions.

In general, metamorphism causes:

Growth of new minerals

Deformation and rotation of mineral grains

Recrystallization of minerals as larger grains

1 the formation and classification of Metamorphic rocks

变质岩的形成

接触变质岩的形成

区域变质岩的形成

2 the description of Metamorphic rocks

◈ Marble （大理岩）

Marble is metamorphosed

limestone or dolomite. Both

limestone and dolomite have a

large concentration of calcium

carbonate (CaCO3). Marble

has many different sizes of

crystals.

Marble has many color variances due to the impurities

( 杂质 ) present at formation. Some of the different colors

of marble are white, red, black, mottled and banded, gray,

pink, and green.

Marble is much harder than its parent rock. This allows it

to take a polish which makes it a good material for use as

a building material, making sink tops, bathtubs, and a car

ving stone for artists. Today, headstones are made from

marble and granite because both of these rocks weather

very slowly and carve well with sharp edges.

◈ Quartzite （石英岩）

Quartzite is composed of sandstone that has been metamorphosed. Quartzite is much harder than the parent rock, sandstone. It forms from sandstone that has come into contact with deeply buried magmas. Quartzite looks similar to its parent rock. The best way to tell quartzite from sandstone is to break the rocks. Sandstone will shatter into many individual grains of sand while quartzite will break across the grains.