Interesting Information on Rocks and Minerals


1. Click on the above animated picture to see how sedimentary rocks are formed.
2. Shows different parts of volcano
 

See how many questions you can score right without looking at the answer first.

What are rocks?

Rocks from the hard outer crust of our planet.  The earth rocks are made up of minerals, and minerals themselves are made up of elements.  Unlike animals and plants, rocks are not alive.  But that does not mean they always stay the same - in fact, they are changing all the time.  Rocks can dissolve, melt, fall apart and even change into other rocks.


 

When can you see rocks being made?

The red-hot sticky lava that flows from an erupting volcano is in fact melted rock or magma, from inside the Earth.  As the lava cools down in the air or in see, it forms solid rocks.  Rocks that are made in this way, such as basalt, obsidian and pumice and pumice, are called igneous rocks (means fiery).  Many different kinds of igneous rocks are formed, depending on how fast the lava cools and what minerals it contains.

Do you know?

Most volcanoes that are round are the oldest. Those are the volcanoes that have already erupted, a lot! The pointy ones may still be young, and may erupt a lot more!

What is the average temperature of lava?

In Hawaii the average temperature is 1171ºC. Mt. St. Helens is about 180-360 º cooler. Yellow lava is hotter than red lava. Yellow is 1200 º Celsius, but red is 700 º Celsius.The temperatures of lava is vary depending on their chemical composition.

Which rock can float in water?

The only rock that floats in water is pumice - a type of igneous rock.  It is made out of frothy lava full of gas bubbles.  As it cools, the bubbles get trapped, creating very light rock.  Pumice is rough, like sandpaper, so people use it for scrubbing dead skin off their feet.

Do you know how Igneous rock is formed?

Igneous rocks are called fire rocks and are formed either underground or above ground. Underground, they are formed when the melted rock, called magma, deep within the earth becomes trapped in small pockets. As these pockets of magma cool slowly underground, the magma becomes igneous rocks.

Igneous rocks are also formed when volcanoes erupt, causing the magma to rise above the earth's surface. When magma appears above the earth, it is called lava. Igneous rocks are formed as the lava cools above ground.

How can mud turn to rock?

Mud that is washed into the sea slowly settles on the sea-bed.  More layers of mud land on top of it, and get squashed down by the weight of the water.  Eventually, over thousands of years, the mud hardens into solid rock.  Rock that forms in this way is called sedimentary rock.  Sediment is anything that settles and collects on the ground or sea-bed.  Any kind of sediment: mud, sand, shells, bits of minerals, or the remains of plants and animals can become sedimentary rock.

How do desert roses grow?

Not many roses grow in the desert, except ones made out of rock.  They grow when mineral crystals form between grains of sand, gluing them together in petal shapes.  They are a kind of sedimentary rock.

Click here to learn about how desert roses are formed in Saudi Arabia.
 

How do rocks change into other rocks?

Rocks change into other rocks if they are squeezed extremely hard.  You could not change a rock much by squeezing it with your hand.  But when movements in the Earth's crust grind rocks together, the enormous pressure forms new minerals.  Rocks that have been changed are called metamorphic rocks.  For example, when mudstone gets squeezed, it turns into the metamorphic rock called schist, containing sparkling crystals of a mineral called mica.

Which cooked rock do sculptors like?

Marble is a kind of metamorphic rock created when limestone under the ground gets heated up by magna.  Marble is usually very beautiful, with coloured streaks and swirls.  It is also soft enough to be carved into sculptures and statues.  (The Taj Mahal in India is a huge tomb made completely out of marble)

How can rocks move mountains?

Sometimes rocks get squeezed together so tightly that they can't be squeezed any more.  Instead they are forced upwards, pressing the Earth's crust into rows of mountains.  The tallest mountains in the world, the Himalayas, were made in this way.  They are up to 8,848m (29,029 ft) high.  As you can imagine, there is a lot of metamorphic rock in the Himalayas.

How does a rock perform a balancing act?

Sometimes a melting glacier or an erupting volcano will move a hard boulder on to the top of an area of softer rock.  Wind and rain wear away the soft rock much faster than the hard boulder.  But the boulder protects the column of rock directly beneath it.  So it ends up balancing on a thin, rocky perch.

What is soft but can cut through rock?

Water.  It easily dissolves hard grains of salt, or cuts a path through sand or mud.  If it has enough time, water can do the same to rock.  As a river flows, it carries away tiny particles of rock from its banks and bed.  Over thousands of years, this can carve away a deep channel called a gorge.  Furthermore, rain, it is not pure water; it is slightly acid, because it dissolves chemicals from the air.  This means that it can slowly dissolve rock.  Acid rain, which has extra acid in it from polluted air, can eat the nose off a stone statue in just a few years.

1 & 2. SPI investigating the power of water that can cut and shape rocks at McKenzie Fall;
3. Testing the impact of water fall; it hits a human to swollen for just one minute.  Given a year time, the hand may got washed off.
 

How can rock act like a sponge?

Some rock can soak up water, just like a sponge.  It can do this because it is full of tiny cracks or holes.  Rocks that can hold water, such as chalk, limestone and basalt are called permeable rocks.  When it rains, water soaks down through the soil and into underground permeable rocks.  Water stored there can be collected with wells and pumps.

How many kinds of minerals are there?

There are about 3,000 different minerals.  But most of them are very rare.  We only use a few hundred of them to make things.  Minerals are usually found in rocks, mixed together with other minerals, so it is not always easy to tell which is which.  Lots of minerals have long, strange names, like skutterudite, demantoid and kornerupine!

Rare minerals: demantoid, skutterudite, kornerupine
 

Can crystals glow in the dark?

Several minerals, such as willemite and datolite, continue to give off a pale glow for a few minutes after a light is switched off.  They have a very important use, they are used to make glow-in-the-dark paint!

Click here to view a gallery of beautiful glow-in-the-dark rare minerals
 

How can you make a crystal disappear?

If you put a cryolite crystal in a glass of water, you won't be able to see it!  This is because cryolite bends light in exactly the same way water does.  So when the cryolite crystal is in water, it looks just like water.

A curious note about cryolite is the fact that it has a low index of refraction close to that of water. This means that if emersed in water, a perfectly clear colorless crystal of cryolite or powdered cryolite will essentially disappear. Even a specimen of cloudy cryolite will become more transparent and its edges will be less distinct, an effect similar to ice in water except that the ice floats.

Cryolite that can disappear in water
 

Can crystals tell the time?

You have probably heard of quartz watches.  Quartz is a very hard mineral, with crystals that vibrate very fast when electricity is applied to them.  The vibrations are so precise and regular that they can be used to count seconds, minutes and hours.

Which mineral can make a fool of you?

If you discovered iron pyrites, you might think you had struck gold.  But although it looks like gold, iron pyrites is not very precious.  It is a common mineral made of iron and sulphur.  So many people have been fooled by it that iron pyrites is known as 'fool's gold'.

What minerals does my body need?

Your body needs about eighty mineral substances.  That is too many to list here, but some of the main ones are copper, zinc, potassium, iron (good for your blood), calcium (good for your bones), fluorine (for healthy teeth), and iodine (without it you get a lumpy neck).  We don't have to dig these minerals out of the ground to eat them.  They are usually found in tiny amounts in our food, fixed in with other chemicals.

Click here to view a mineral and vitamins intake guide by RDA
 

Which minerals are poisonous?

Most minerals are inedible, but some are also deadly poisonous.  These include lead, mercury and orpiment.  Orpiment contains arsenic, a famous poison that was once used to kill rats.  Other minerals, such as asbestos, are poisonous if you breathe in their dust.  Even essential minerals are bad for you if you have too much of them.  Your body needs copper, but a large amount would make you very ill.

Click here to view a guide about lead poisoning
 

Is the lead in a pencil really lead?

No, it is a different mineral called graphite.  Like coal and diamonds, graphite is made out of carbon.  It is not poisonous, so sucking your pencil will not give you lead poisoning.  But still, please don't try.

 

What minerals make a light bulb work?

When you switch on a light, electricity flows along copper wires and into a filament made of tungsten (which comes from a mineral called wolframite).  The filament glows and shines through a light bulb of glass (made from quartz).  Mineral teamwork!

Why do some minerals smell?

Minerals usually smell because they react with the air or with water to produce a gas, which you can smell as it wafts away.  For example, minerals that contain sulphur often smell like rotten eggs.  Minerals that contain arsenic smell a bit like garlic.