rocks and fossils rocks and fossils Granite Gabbro What do I look like? What do I look like?

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1 Granite Gabbro Large crystals Pale colour Doesn t scratch easily with a paperclip (hard!) Crystals arranged randomly Medium sized crystals (look with a magnifying glass!) Grey colour Doesn t scratch easily with a paperclip (hard!) Crystals arranged randomly Crystals different sizes

2 Gabbro Granite Formed when liquid rock (magma) cools quite slowly underground. This rock is very hard. This makes it very useful as rock armour, it is placed along a coast line to protect the land from erosion by the sea. Formed when liquid rock (magma) cools very slowly underground. This rock is very hard but also nice looking once it is polished. This makes it a useful material to make kitchen worktops out of because it can withstand hard usage and still look pretty.

3 Dolerite Basalt Small crystals (look with a magnifying glass!) Black colour Scratches with a paperclip Very small crystals Black or greyish black colour Scratches with a fingernail Gas holes filled with a white mineral

4 Basalt Dolerite Formed when liquid rock (magma) cools fast above ground, often when erupted from a volcano. This rock is the most common kind of rock in the Earth s crust. In fact the ground under all the world s oceans are made of basalt! Formed when liquid rock (magma) cools underground, while it is being channelled up to a volcano. This rock can form very steep cliffs once it is exposed at the Earth s surface, this is because it is very hard and is only worn down very slowly by the wind and rain.

5 Gneiss Marble Medium sized crystals Pale colour Doesn t scratch easily with a paperclip (hard!) Crystals arranged in bands Medium sized crystals Pure white Sugary texture Doesn t scratch easily with a paperclip (hard!) Crystals all the same size

6 Marble Gneiss Formed when limestone is buried deep underground and put under high temperature and pressures. This rock is thought of as extremely beautiful and it comes in all sorts of colours. You will often see Ancient Greek and Roman statues made from marble. Formed when granite or sedimentary rock is buried deep underground and put under very high temperature and pressure. This rock can have patterns that let you see how the original rock was bent and twisted. It is also the oldest type of rock in Britain, you can find gneiss is Scotland that is 3,000 million years old!

7 Schist Slate Medium sized crystals Silver colour Very shiny when held to the light Very small crystals (you can t see them with a magnifying glass!) Grey to purple colour Scratches with a penny Often thin and flat in shape (you might see some layers!)

8 Slate Schist Formed when mudstone or shale is buried deep underground and put under low temperature and pressures (but higher than the surface!). This rock is useful as it is hard, it splits into thin sheets and is impermeable (it doesn t let liquid pass through). For this reason it is often used to make roof tiles for houses. Formed when mudstone or shale is buried deep underground and put under very high temperature and pressures. This rock can grow gemstones! Garnet crystals can form in schists, these crystals are very pretty and have been used for jewellery since the Roman times.

9 Mudstone Limestone Very small grains (you can t see with a magnifying glass!) Dark brown to black colour Scratches with a fingernail (it s very soft!) You can sometimes see bedding planes (layers in the rock) Very small grains (usually can t see any with a magnifying glass) Grey or cream coloured Fossils common (some of these might be shiny like crystals) Scratches with a paper clip

10 Limestone Mudstone Formed in shallow oceans when coral and sea shells are crushed up or dissolved and build up in layers. These layers are squashed together or compacted to make this kind or rock. This rock was made during the Carboniferous period 360 to 300 million years ago, before dinosaurs evolved, when huge swamps and rainforests covered lots of the Earth. Formed in deep oceans when mud falling to the seabed builds up in layers. These layers are squashed together or compacted to make this kind or rock. This rock was made during the Jurassic Period 200 to 145 million years ago, when sea levels were much higher and oceans covered lots of the Earth.

11 Sandstone Desert Sandstone Small grains (you can see with a magnifying glass!) Light brown, sandy colour Grains can be shiny in the light Doesn t scratch easily with a paperclip (hard!) Medium sized grains Red colour Grains can glitter in the light Doesn t scratch easily with a paperclip (hard!)

12 Desert Sandstone Sandstone Formed in a desert where sand grains are blown by the wind and build up. All of the sand grains are squashed together or compacted to make this kind or rock. This rock was made during the Triassic period 250 to 200 million years ago, before dinosaurs evolved, when huge deserts covered lots of the Earth. Formed in the mouth of a river (estuary) when sand that is carried by the river and dropped builds up in layers. These layers are squashed together or compacted to make this kind or rock. This rock is permeable (lets liquid pass into it) this means it can be very good at storing water underground.

13 Oolitic Limestone Conglomerate Medium sized grains Cream colour Can scratch with a penny Contains small white balls of limestone Lots of different sized grains Pebbles and sand cemented together Sand has brown colour, pebbles are lots of different colours Can scratch with a penny Fossils common

14 Conglomerate Oolitic Limestone Formed in a river when pebbles and sand are dropped to the river bed and build up in layers. These layers are squashed together and compacted to make this kind of rock. This rock was made during the Jurassic Period 200 to 145 million years ago, when sea levels were much higher and ocean covered lots of the Earth. Formed in shallow oceans when coral and sea shells roll around the sea floor and make little balls called ooids which build up in layers. These ooids are squashed together or compacted to make this kind or rock. This rock is permeable (lets liquid pass into it) this means in the right conditions it is very good at storing oil underground. We find oil in oolitic limestones in the Middle East and the USA.

15 Chalk Very fine grains Pure white colour Can scratch with a penny Chalky texture

16 Chalk Formed in oceans when tiny sea creatures called algae die, fall to the seabed and build up in layers. These layers are squashed together or compacted to make this kind of rock. This rock was made during the Cretaceous Period 145 to 65 million years ago, the golden age of dinosaurs.