Minerals
What is a mineral? Minerals are the building blocks of rocks. They are non-living, solid and are made of atomsof elements. There are many different types of minerals and each type is made of specific groups of atoms. The atoms are arranged in a network called a crystal lattice. The lattice of atoms is what gives a mineral its crystal shape. Different types of minerals have different crystal shapes. Most minerals can grow into crystal shapes if they have enough space as they grow. But there are often so many different crystals growing in the same little area that they all compete for space and none of the crystals is able to grow very large. There are two main ways that new crystals of minerals grow. Some minerals form when molten rock, called magma below a planet’s surface and lava abovethe surface cools and atoms bond together into mineral crystals. There are six ways to tell a mineral apart from another. Scroll down for more information about the different ways to detect the different types of minerals.
Streak
A streak is one way to detect a mineral. When you rub a a mineral across a piece of unglazed porcelain tile it usually leaves a streak. The streak is the colour of the powdered form of the mineral. A porcelain tile has a hardness value of 7. Minerals that have a hardness greater than 7 do not leave a streak on the tile. Graphite is a mineral used in pencils. Pencil marks are graphite streaks that are soft enough to be left on a piece of paper. A streak test is one way to identify whether a mineral sample is gold or pyrite. Gold leaves a golden streak and pyrite leaves a greenish-black or brownish-black streak.
Hardness
How would you know what is the hardest mineral and the softest mineral? Well there is something called the "Moh's Hardness Scale". Some of you have heard of this, well I am going to tell you a little bit more about it. First you need to know what a Moh’s scale does. A Moh's Scale measures the hardness of a mineral and also helps identifies the mineral. The Moh’s Scale has a scale that measures from 1-10. For example the Talc is the sofest mineral and on the scale it would be a 1. The mineral is so soft you could scartch it just with your fingernail, unlike the diamond which is the hardest mineral on the scale it is very difficult to scratch.
Lustre
Some minerals, such as gold and silver, appear shinny. (Another clue to their identity) Other Minerlas appear dull. The shininess or lustre, of a mineral depends on how light is reflected from its surfac. If a Mineral shines like a polished metal surface, it is said to have a metallic lustre. If a mineral does not shine like a metal, it has a non-metallic lustre.
Cleavage and Fracture
The way a mineral breaks apart is another clue to its identity. If a mineral breaks along smooth, flat surfaces, it is said to have cleavage. Mica is an example of a mineral with cleavage. Separating the layers of mica is like separating the pages in a book. Not all Minerals have cleavage. Minerals that break with a rough or jagged edges have fracture. Quartz is an example with fracture. In order to examine cleavage and fracture, you need to look at a freshly broken surface of a mineral.
Colour
The colour of the mineral is the most attractive property of a mineral. The colour of a mineral can also be a clue to it's identity. However, colour alone cannot identify a mineral. Two or more minerals may have the same colour. Also, one of the same minerals may be found in many different colours.
Crystal Structure
The crystal structure is an important physical property of minerals. A crystal has straight edges, flat side and regular angles. Most of the minerals in Earth's crust develop into beautiful shapes according to the six different crystal systems. Sometimes the crystal structure is visible in a mineral, such as the galena. Often, the crystals are too small to be seen.
Rocks
Hmm... The odd shaped things that are usually found on the ground. You’re probably thinking what’s so cool about rocks. Well you’ve came to the right place to learn about interesting things about rocks you may have never known about before. First of all there are three different types of rocks, Igneous, Sedimentary and Metamorphic. They are categorised by these three groups because the way it was formed. Rocks are also made up of one or more minerals. Scroll down for more information about the three types of rocks.
Igneous rocks
Igneous rocks form when hot magma or lava cools and becomes solid. Geologists classify igneous rocks based on whether it was formed above or below the Earth’s surface. If the rock was formed below the Earth’s surface geologists call it “Intrusive rock”. Intrusive rock cools very slowly and it could take a long time to cool. If the rock was formed above the Earth’s surface geologists call it “Extrusive rock”. Extrusive rock cools very quickly.
Sedimentary rocks
Sedimentary rocks are made from sediments and/or by chemical reactions. Sediments are loose material, such as bits of rocks, minerals, plants and animals. Water, wind and ice can move sediments around until it finds a place to settle. When sediments slowly settles on top of other sediments it forms layers. Sediment rocks usually are formed in oceans or lakes where the larger, heavier sediments settle first. Each layer is squeezed together by the weight above it. The process of the layers being squeezed together is called compaction. The minerals in some rocks dissolve as water soaks into the rocks. The dissolved minerals form natural cement that sticks the larger piece of sediment together. The process in which pieces of sediment are held together by another material is called cementation. Many sedimentary rocks are formed by compaction and cementation. Other sedimentary rocks are formed by chemical changes. Sedimentary rocks commonly contain fossils.
Metamorphic Rocks
If you ever see a rock with many shiny particles and many layers you may have found a metamorphic rock. A metamorphic rock is made when heat, pressure or fluids change one type of rock into another type of rock. Metamorphic rocks can be made from igneous and sedimentary rocks and form other metamorphic rocks. The formation of a metamorphic rock is a long, slow process.
Metamorphic rocks are always formed below the Earth’s surface, where heat and pressure are very high. Hot watery fluids can flow into igneous, sedimentary or metamorphic rock and change the rock both physically and chemically. The rock that has been changed into a metamorphic rock is called the parent rock. Depending on the amount of pressure and temperature applied one parent rock can change into several different metamorphic rocks. For example sedimentary rock called shale can change into slate. If more pressure and heat applied, the slate could change into schist and eventually gneiss.
Metamorphic rocks that have layers are called foliated. Foliated means having thin, like leaf layers. Some metamorphic rocks do not have layers. When the mineral structure changes the rock did not form layers. Marble and quartzite are metamorphic rocks that usually do not have layers. Metamorphic rocks that do not have layers are called non-foliated. The parent rock can change completely that the metamorphic rock has no longer looks like it. The two rocks have common characteristics but geologists know that they are related.
Metamorphic rocks are always formed below the Earth’s surface, where heat and pressure are very high. Hot watery fluids can flow into igneous, sedimentary or metamorphic rock and change the rock both physically and chemically. The rock that has been changed into a metamorphic rock is called the parent rock. Depending on the amount of pressure and temperature applied one parent rock can change into several different metamorphic rocks. For example sedimentary rock called shale can change into slate. If more pressure and heat applied, the slate could change into schist and eventually gneiss.
Metamorphic rocks that have layers are called foliated. Foliated means having thin, like leaf layers. Some metamorphic rocks do not have layers. When the mineral structure changes the rock did not form layers. Marble and quartzite are metamorphic rocks that usually do not have layers. Metamorphic rocks that do not have layers are called non-foliated. The parent rock can change completely that the metamorphic rock has no longer looks like it. The two rocks have common characteristics but geologists know that they are related.
Rock Cycle
When the lava dries and becomes an igneous rock it can become both a sedimentary rock and a metamorphic rock. If it becomes a sedimentary rock ,erosion will break it apart into sediments. The sediments will be effected by either compaction or cementation, resulting in the making of a sedimentary rock. If it were to turn into a metamorphic rock then heat and pressure will push it down below the surface. Then hot watery liquids will change it into a metamorphic rock. A metamorphic rock can turn into a sedimentary rock or an igneous rock. If it were to turn into an igneous rock then the rock would melt from all the heat below the earth and it would become magma. Then like all igneous rocks it would either explode from the volcano and dry on land, or it would stay below the earth and dry there, both ways it would become an igneous rock. If it were to turn into a sedimentary rock, erosion would cause it to break apart and become sediments and then compaction and cementation would effect it. Finally it would become a sedimentary rock.
A sedimentary rock could become all three even another sedimentary rock. It becomes those three rocks
A sedimentary rock could become all three even another sedimentary rock. It becomes those three rocks