DK-EyeWonder-RocksAndMinerals

Eye Wonder 4-5 Rocky Earth 6-7 A volcanic beginning 8-9 Making of a rock 10-11 Igneous rock 12-13 Sedimentary rock 14-15 Metamorphic rock 16-17 Rocks from space 18-19 Hidden beauty 20-21 Breakdown 22-23 Carving a path 24-25 Crystals 26-27 What a gem! LONDON, NEW YORK, MUNICH, MELBOURNE, and DELHI Contents First published in Great Britain in 2004 by Dorling Kindersley Limited 80 Strand, London WC2R 0RL 2 4 6 8 10 9 7 5 3 1 A Penguin Company Copyright © 2004 Dorling Kindersley Limited, London A CIP catalogue record for this book is available from the British Library. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of the copyright owner. ISBN 1-4053-0090-6 Colour reproduction by Colourscan, Singapore Printed and bound in Italy by L.E.G.O. see our complete catalogue at www.dk.com Written and edited by Caroline Bingham Designed by Helen Chapman Publishing manager Susan Leonard Managing art editor Clare Shedden Jacket design Chris Drew Picture researcher Sarah Stewart-Richardson Production Shivani Pandey DTP Designer Almudena Díaz Consultant Kim Dennis-Bryan PhD, FZS With thanks to Victoria Long for design assistance. 28-29 Precious metals 30-31 Get that metal! 32-33 Using rocks in art 34-35 Rocks in history 36-37 Building rocks 38-39 A touch of mystery 40-41 History in a rock 42-43 Hunting for rocks 44-45 What does it make? 46-47 Glossary 48 Index and acknowledgements 4 car computer clothes te lephone jewellery you and me! house Rocky Earth Rocks and minerals are important. They make up much of our planet and are mined to provide many of the things around us, from cars to computers. Even your body contains minerals that keep you alive. toothpaste Store cupboard The things we use in our everyday lives come from our planet, Earth. The raw ingredients are all taken from the crust. We cannot drill any deeper. Most of the crust and mantle is made from lots of different rocks, all squashed together. 5 Let’s make a rock Rocks are made up of crystals of minerals. Different amounts of minerals make up different rocks (though some rocks are made from just one mineral). Let’s make shampoo What forms the shampoo you use on your hair? Minerals, including those below! Earth’s crust is between 5 and 68 km (3 1⁄2 and 42 miles) thick. Quartz (grey) Scientists believe the Earth was born about 4,600 million years ago. + + = + + = quartz crystals feldspar crystals mica crystals granite (a type of rock) coal tar lithium clay selenium shampoo M antle Earth’s crust Outer core Core Mica (black) Feldspar (pink and white) •Your body contains more than 60 minerals. Nine of these are essential for life. •Some minerals take thousands of years to form. Some form in minutes. Mineral facts Squeeze clay in your hands and it oozes between your fingers. This is a little like what happens inside a volcano. The pressure grows until the volcano erupts. Whoosh! It is the first step in the formation of new rocks. A volcanic beginning Th e m ag m a is fo rc ed up in sid e th e vo lc an o. Magma (molten rock) chamber. Previous eruptions have formed a cone- shaped exterior. No place for a rock? Deep, deep under the Earth’s crust it is hot enough to melt rock. This molten rock sometimes builds up in chambers and bursts through weak spots in the Earth’s crust. When magma leaves a volcano, it is called lava. Shiprock Shiprock Pinnacle is all that remains of an ancient volcano. It is the hardened core. Just a cliff? The eruption of a volcano can create deep layers of ash, dust, and rock at its base. It changes the landscape. Volcanic debris ranges from dust and ash to rocks the size of houses. Shiprock Pinnacle in New Mexico was once a plug of magma filling the chimney vent of a volcano. Avalanche of rock A volcano erupts with such power that sometimes the eruption destroys a part of the volcano. Huge rocks shoot into the air. Sh ip ro ck Pi nn ac le i s named after a ship as it looks a little like one. Do you think that all rocks look the same? In fact, there are many different kinds of rocks, but they can be divided into three basic types, which are being formed (and destroyed) as you read this book. Making of a rock In the beginning Earth’s first rocks were igneous rocks. These form from molten rock that has cooled and hardened. Chipping away One way sedimentary rock forms is when pieces of rock are carried to the sea where they create huge piles of sediment. After thousands of years these cement together. Molten volcanic rock cools to form igneous rock. Sedimentary rock Sediments are 9 Sediment settles on the bottom of seas, rivers, and lakes. builds up in la yers. Getting hotter Rub your hands together and they get hot. Metamorphic rock forms when rocks are squeezed and heated deep under the Earth’s crust. The pressure and heat as granite is forced up causes the development of the metamorphic rock marble. Granite Dee p unde r the earth, rocks are being sq uashed and heated. ROCKING AROUND Over thousands of years, each type of rock can change into one of the others depending on what happens to it, from igneous to sedimentary to metamorphic. Marble squashed together. 10 Igneous rocks form the greatest part of Earth’s rocky crust, but can also be seen in the land around us. A famous igneous rock landscape is the Giant’s Causeway in Northern Ireland. Igneous rock Pumice is an igneous rock from the heart of a volcano. Pele’s hair looks like hair! It forms from sprays of lava. Obsidian has a shiny surface. It contains a lot of glass. Built to last The most common igneous rock is granite. It is incredibly strong, and has been used for building for thousands of years. From hair to glass A volcano produces a great variety of igneous rocks. Just take a look at the three examples shown above. London’s Tower Br idg e u ses gr an ite . Pu mi ce sto ne is t he onl y floating rock. 11 Giant’s Causeway The Giant’s Causeway in Antrim, Northern Ireland, formed when basalt lava cooled and shrank. This type of lava can create hexagonally shaped columns. Legends say g iants used the ca use way as step ping sto nes. •“Igneous” comes from the Latin word for “fire”. •The more slowly that a rock cools from its molten form, the larger the crystals. •Granite cools slowly and has large crystals. Obsidian, which cools quickly, has small crystals. Igneous facts Towering chalk cliffs are an amazing example of sedimentary rock. They are formed from the shells and skeletons of microscopic sea creatures. Just imagine how many are needed to build a cliff. Sedimentary rock One by one The sea creatures that break down to create chalk are tiny. It’s thought that these cliffs grew by 0.5 mm (0.02 in) a year – that’s about 180 of these creatures piled on top of one another. In places, these cliffs are 90 m (300 ft) high. Year 1...From plant to rock Another way in which sedimentary rocks form is by the breakdown of plants. As they are buried, they are squeezed together, eventually forming coal. 12 Movem ents in the Ear th’s cru st have l ifted the cliffs out of the sea. From plant matter... to peat... Let’s play Do you like to play in golden sand? This is a sediment. Left for thousands of years, it may eventually form sandstone, a sedimentary rock. Rocks are continually eroded, over millions of years, to produce sand. at 90 million years... and after 360 million years. A s well as tiny shells, it can contain large fossils. Chalk takes millions of years to form . All mixed together This sedimentary rock has formed when pebbles have cemented together, a bit like a cake mix. ...to coalto lignite... to bituminous coal... 13 14 “Metamorphic” comes from the ancient Greek words, meta (meaning change) and morphe (meaning form). When rocks are heated or compressed, this type of rock forms. Metamorphic rock Marble magic Marble is a beautiful metamorphic rock. It is mined by being cut into huge blocks with strong cutting wires. A peek at slate The metamorphic rock slate forms from mud and a rock called shale. The shale has been squeezed and compressed as mountains are pushed up. Slate splits easily into sheets. Underground changes One way metamorphic rocks form is when mountains are pushed up out of the Earth’s crust. Mountains and hills surround this old slate quarry. Each block weighs tho usands of t onnes. Marble can be carved into statues. 15 The dark host rock contains swirls of a lighter coloured rock. A shimmering palace Polished marble looks stunning when used for building, and perhaps the world’s most famous marble building is the Taj Mahal in India. The marble shimmers in the sun. Icecream swirls When rocks are heated, parts may begin to melt and run through a “host” rock. This makes swirly patterned metamorphic rock. The rock is called migmatite. Water cools the cutting equipment in a quarry. Marble is formed from limestone. 16 We cannot see it, but about 23 tonnes (25 tons) of dust rain down on Earth every day. This fine dust arrives from space. Occasionally a rock from space hits Earth; this is called a meteorite. A meteorite hit Meteorites are pieces of rock or metal that hit Earth. Some have broken off asteroids, large chunks of rock that orbit the Sun between Mars and Jupiter. Most are fragments of comets. Rocks from space What’s inside? Meteorites from asteroids contain metals such as iron as well as rocks. Those from comets contain more rock than metal. M eteorites hit Earth. Meteors burn up above it. There is evidence that a massive meteorite hit Earth 65 million years ago, causing the dinosaurs to die out. C om ets pass on by. 17 The pitted surface is created by the immense heat as the meteor “rubs” against the atmosphere. What’s that hole? If a large meteorite hits Earth it can form a crater, changing the surroundings where it lands. It would take you about 30 minutes to walk across this meteorite crater in Australia. I spy a shooting star Meteors or shooting stars can be seen as they burn up in Earth’s atmosphere, usually more than 80 km (50 miles) above our heads. M ost m eteors are the size of a small peb ble. A large meteorite may be travelling at 40,000 km/h (25,00 0 mph ) whe n it hits . This crater is so old that trees have grown in its base. Just passing Comets are a bit like huge snowballs, but made of ice, gases, and dust. They orbit the Sun, developing long tails as they near Earth. A comet’s tail is narrow but it can stretch for hundreds of kilometres. ONCE IN A LIFETIME One of the most famous comets, Halley’s, was included in the Bayeux Tapestry, which was stitched more than 900 years ago. This comet passes Earth just once every 76 years. It last passed us in 1986. 18 Brrrr! A cave is a damp, dark, chilly place. However, if you are lucky enough to visit a large cave that has been lit and opened to visitors, you’ll discover incredibly beautiful shapes in the rocks. Hidden beauty Water damage Over the course of thousands of years, a constant flow of water will eat away at a solid area of rock. After 100,000 years, this may have formed a small cave, which will continue to grow. This cave has opened into a vast cavern. This stream falls further than the length of a football pitch. Soft centre Have you ever eaten a hard sweet with a soft centre? Volcanic caves can form when soft lava pushes on through a hardened outer layer. Build it up Cave formations can be amazingly complicated. These slender shapes have built up gradually, as drops of water have deposited traces of a mineral called calcite. A funny shape Stalactites hang down while stalagmites grow up. It can take 1,000 years for these formations to grow less than a centimetre. The se vo lcanic caves were once mined for millstones. The tallest stalagmite in the world is the height of a six-storey house. Rock formations in caves build up drip by drip. 19 20 Rocks are not as permanent as you may think. From driving rain to frothy seas, when rocks are exposed to wind, water, glaciers, or shifts in temperature, changes begin to happen. Breakdown Attack by wind and water Hoodoos are columns of soft sandstone topped by harder rock caps. The cap has protected the rock beneath it from being washed away by heavy downpours of rain. Attack by sea A long time ago, these stacks were a part of Australia’s coastline, but they have been cut off from the coast after an ongoing battering from the sea. The layers that make up the sedimentary rock in these hoodoos can be clearly seen. T he su rr ou nd in g ro ck ha s be en w as he d aw ay . 21 Attack by acid rain Pollution from cars and lorries attacks rock. The gases are carried in rainwater to make acids that eat into rock – as shown by the damage to this sculpture. Attack by river Over millions of years, the Colorado River has carved its way down into America’s Grand Canyon, exposing rock faces 1,829 m (6,000 ft) deep. Erosion causes sediment. If a hoodoo loses its protective cap, the structure will soon begin to wear away. Hoodoos form spectacular shapes, all clustered together. Erosion facts •The wearing away of a landscape is known as erosion. •Plants add to rock erosion as their roots burrow their way into cracks in rocks. •When rocks are broken down where they stand, it is known as weathering. A glacier is a huge mass of slow- moving ice. Born as snow builds up at the top of a mountain, it begins to force its way forward, picking up rocks and boulders as it moves. Carving a path Slow progress Glaciers usually creep just a few centimetres a day. They end lower down the mountain where the water melts away, or at the coast where large blocks break off. 22 The for ce of a glac ier is e nou gh to crumble rock. From rock to flour! The sides and base of a glacial valley are covered with plenty of scrapes and scratches. This scraping produces fine grains of rock, known as rock flour. Sprinkle on the colour! Mountain lakes are often incredible shades of turquoise blue. This is because of the rock flour fed into them by a melting glacier. A glacier carves a deep valley as it moves forwards. Tiny particles of rock in the water catch the light in a certain way. Some is deposite d in mountain lakes.R ock flour is carr ied on down the glacier. Adding the stripes As a glacier works its way forward, it picks up all sorts of rocks and sediment. This forms darker streaks on the surface of the glacier. FANCY AN ICE LOLLY? The word crystal comes from the Greek word kyros, which means “icy cold”. The ancient Greeks thought quartz crystals were made of ice that had frozen so hard it could not melt. 24 Have you ever cut a paper snowflake? Snowflakes are made from small ice crystals that collide and stick together. Crystals also form in rock, and can be cut and polished. From little to big The tiny crystals that make up the endless golden sands of a desert are made of quartz. Quartz can also form gigantic crystals. The largest rock crystal was about 6 m (20 ft) long! Beautiful colours Many crystals come in a rich range of colours. This purple amethyst is a form of quartz. It can also be lilac or mauve. Crystals su rr ou nd in g co nd iti on s rem ain the sam e. C ry st al s c on tin ue to gr ow as l ong as t he Is it a thread? Not all rock crystals are hard. This is a crystal called tremolite. It forms flexible strands similar to the fibres in material. But you wouldn’t be able to sew with tremolite. It could make you ill. The power to heal? Some people believe that certain crystals have special powers. Jade is thought to help relaxation, lapis lazuli to help friendships. Seems a bit salty Salt may not seem like a rock, but it is a crystalline rock. In Bolivia there is even a hotel built from salt bricks, including the chairs and tables! Strands of tremolite have a silky, translucent look because light passes through the fibres. 25 Salt crystals form wh en sea wa te r e va po ra te s. Am et hy st is pr ize d fo r i ts co lo ur . Polished jade Lapis lazuli From sparkling diamonds to rich red rubies, some rocks are valuable and are known as gems. They are mined from the Earth at huge expense, cut and polished, and worked into jewellery. Shine on A cut stone reflects more light, just like this diamond. A cut diamond may have as many as 58 flat sides. Diamond is the hardest mineral of all. Garnet Amethyst Aquamarine Diamond Emerald Gemstones such as rubies can be rounded and polished or cut. What a gem! Not just a rock Most gemstones come from rocks. Just imagine that you were lucky enough to find this rock, with its red rubies. Which are you? Do you know your birthstone? Some people believe it is lucky to wear a gem that is linked to their month of birth. January February March April May 26 A ge m is a st one that has a beautiful colour. 27 Pearl Ruby Peridot Sapphire Opal Topaz Turquoise Pearl forms in certain shellfish, especially oysters. Amber is the fossilized resin of fir trees. It sometimes contains trapped insects. Jet is the fossilized remains of wood. Coral, the skeletal remains of tiny sea creatures, grows in warm seawaters. Are all gems rocks? Most gems come from rocks, but there are four that don’t: pearl, amber, jet, and coral. These are softer than rock gems and are usually polished and not cut. June July August September October November December Diam ond com es fro m th e G re ek w or d ad am as , w hi ch m ea ns “i nv in ci bl e” . More than 250 tonnes (275 tons) of rock are blasted for every 0.2 g (0.007 oz) diamond retrieved. 28 Gems are not the only treasures hidden deep within our rocky planet. Precious metals such as gold, silver, and platinum have long been mined and used to make objects of great beauty. Precious metals Gold Bangkok in Thailand is home to the Golden Buddha, a religious statue made of solid gold. It weighs 5.5 tonnes (6 tons) – the weight of a small truck. Gold is sometimes found in veins of quartz. 29 Platinum Platinum is the most expensive metal of all. No wonder it was used to make this crown, part of the British Crown Jewels. Silver Seven hundred years ago silver was more valuable than gold. This soft metal was used for coins and jewellery – and for statues such as this Hindu figure. Silver is sometimes found with a delicate frond-like shape. This rare platinum nugget weighs the same as 10 apples. 30 Some metals are held inside rocks as minerals – the rock that holds the mineral is known as the ore. Some ores are near the surface, some are deep underground. Get that metal! Let’s make a hole Most metals are collected from open-cast mines. This means that the surface is blasted and tonnes of rock are removed, truckload by truckload. Copper pipe Some of the copper extracted from the mine below will be used to make copper pipes. Boom! An open-cast mine is a noisy place. The miners constantly blast away at the rock so they can take it away and extract the metal. 31 Mix them together... Metals are often melted down and joined to other metals to make a stronger metal, an alloy. ...to get When copper and tin are mixed together, they produce bronze, which