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Classification with Rocks and Minerals

Picture taken from, ESListserv [email protected], origional source unknown

Support for Cornell Center for Materials Research is provided through NSF Grant DMR-0079992 Copyright 2003 CCMR Educational Programs. All rights reserved.

IGNEOUS ROCK FORMATION

Molten rocks called magma is found under high temperatures in the Earth's interior. Some of this molten rock remains inside the Earth and some is ejected as lava onto the Earth's surface during volcanic eruptions. When the molten rock cools and solidifies, it becomes mineral crystals. The process of forming mineral crystals is called crystallization. As the mineral crystals form, they join together or interlock into masses of igneous rocks.

Igneous rocks include:

Granite, Basalt, Obsidian, Pumice

Support for Cornell Center for Materials Research is provided through NSF Grant DMR-0079992 Copyright 2003 CCMR Educational Programs. All rights reserved.

METAMORPHIC ROCK FORMATION

The temperatures and pressures inside the Earth are much higher than those on the Earth's surface. When rocks are subjected to greater heat and pressure inside the Earth, they are changed into rocks, which are different from the original. This change occurs while the original rocks are still in a solid state. The new rocks that are groomed by changing existing rocks under heat and pressure are called metamorphic rocks.

Metamorphic rocks include: Quartz, Amethyst, Marble,

Slate, Gneiss, Graphite, Coal

Support for Cornell Center for Materials Research is provided through NSF Grant DMR-0079992 Copyright 2003 CCMR Educational Programs. All rights reserved.

SEDIMENTARY ROCK FORMATION

One way Sedimentary rocks are formed is by; Compacting Sediments

Fig 1: Compaction of sediments

Sediments may be rock particles such as mud, sand or pebbles, which are usually deposited in the sea by rivers and waves. They can also be remains of living things such as plants and animals. Gradually, over thousands or even millions of years, these sediments accumulate layer-bylayer, forming thick deposits on land or on the sea floor (SEE Fig 1). The weight of the overlying sediments will compact those found below. Over time, the compacted sediments become sedimentary rocks. Sometimes, these sedimentary rocks may be uplifted as a result of plate movements forming mountain, eg. The Himalayas. Sedimentary rocks include: Limestone, Jasper,

Gypsum, Conglomerate, Sandstone

Support for Cornell Center for Materials Research is provided through NSF Grant DMR-0079992 Copyright 2003 CCMR Educational Programs. All rights reserved.

SEDIMENTARY ROCK FORMATION

Another way Sedimentary rocks are formed is by; Crystallization from Dissolved Minerals

Fig 2: Crystallization of dissolved minerals in a shallow part of the sea.

The process of forming crystals from dissolved minerals usually occurs in the shallow parts of the sea or in lakes in desert areas where evaporation is much higher than precipitation. The sea or lake contains dissolved minerals such as calcium bicarbonate and calcium sulphate. As evaporation takes place, water is lost and the dissolved minerals from crystals which settle on the bottom of the sea of lake (SEE Fig 2). As evaporation continues, more crystals from and accumulate on the sea or lake floor, becoming sedimentary rocks.

Support for Cornell Center for Materials Research is provided through NSF Grant DMR-0079992 Copyright 2003 CCMR Educational Programs. All rights reserved.

Most common minerals can be identified by inspecting or testing their physical properties

Color (use your eyes)

Usually, we notice the color of a mineral first. Keep in mind that color by itself isn't enough to identify a mineral. Chemical impurities often change the color of a mineral without changing its basic make-up.

Streak (use porcelain plate)

When a mineral is rubbed firmly across an unglazed tile of white porcelain (a streak plate), it leaves a line of powder. This is called the streak. The color of the streak is always the same, whether or not the mineral has impurities. For example, quartz leaves a white streak, whether it's violet (amethyst), pink (rose quartz), or brown (smoky quartz).

Magnetic (use magnet)

If a mineral is magnetic, a magnet will stick to the mineral. Magnetism is caused by the presence of iron and is useful in identifying iron oxides

Hardness (use your fingernail, the penny and the nail)

The Mohs' hardness scale places ten common or well-known minerals on a scale from one to ten. One is the softest mineral and ten is the hardest. These are the minerals used in the Mohs' hardness scale: Mohs' Hardness Scale 1 Tal c 2 Gypsu m 3 Calcit e 4 Fluorit e 5 Apatit e 6 7 8 9 10 Diamon d Feldspa Quart Topa Corundu r z z m

Use the tools from your test kit to determine the hardness of your samples. *(Your kit does not include the glass or the emery cloth do your best to approximate)

Common Objects and Their Hardness Values 2.5 Fingernail 3.5 5.5 6.5 8.5 Penny Glass Nail Emery cloth

If an unknown sample cannot be scratched by your fingernail (2.5) but can be scratched by a penny (3.5), then it's hardness is between 2.5 and 3.5.

Support for Cornell Center for Materials Research is provided through NSF Grant DMR-0079992 Copyright 2003 CCMR Educational Programs. All rights reserved.

1- Hemitite

2-Quartz (Milky)

3-Schist (Mica)

Support for Cornell Center for Materials Research is provided through NSF Grant DMR-0079992 Copyright 2003 CCMR Educational Programs. All rights reserved.

4-Talc

5-Marble (White)

6-White Granite

Support for Cornell Center for Materials Research is provided through NSF Grant DMR-0079992 Copyright 2003 CCMR Educational Programs. All rights reserved.

7-Pumice

8-Galena

9-Magnetite (Lodestone)

Support for Cornell Center for Materials Research is provided through NSF Grant DMR-0079992 Copyright 2003 CCMR Educational Programs. All rights reserved.

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