Minerals & Rocks

2/27/2013 – 2/28/2013

Bell Ringer 2/27

Create a K/W/L chart for minerals & rocks. Fill in the “K” column – what do you already know about minerals and rocks?

Rock Classification Activity

With a partner, your job is to take the rocks in your kit and come up with a way of sorting them.

When you have sorted your rocks, write a short paragraph about how you decided to sort them. (Did you base it on color? Shape? Size? Texture? Some other criteria?)

Minerals

A mineral is a naturally occurring, inorganic solid with a definite crystalline structure, and a definite composition.

→ Most minerals are nonmetallic (e.g. graphite, quartz, halite).

→ HOWEVER, gold, silver, and copper also meet the definition of mineral (and they are metals).

→ Gems are valuable, highly priced minerals that are rare or difficult to obtain.

Rocks

A rock is a mixture of one more more minerals. They can also be a mixture of mineraloids, glass, or organic particles.

Types of Rocks

Igneous rocks

Metamorphic rocks

Sedimentary rocks

Igneous Rocks

An igneous rock is a rock that formed as molten material cooled

Q: What does the word 'igneous' remind you of?

As lava or magma cools, it becomes solid (like our play-doh volcanoes at the beginning of the school year).

Many crystals of various minerals form from the cooling of lava or magma. The crystals grow together and form solid igneous rock. More than 90% of the Earth's crust is made of igneous rocks.

Intrusive Igneous Rocks

Intrusive igneous rocks are formed by magma that cools beneath the Earth's surface. This process can take thousands of years.

They are found at the surface once rock and soil that used to cover them is removed by erosion.Compression & tension forces with the Earth sometimes force intrusive igneous rock to the surface.

Examples: granite, gabbro, diorite

Extrusive Igneous Rocks

Extrusive igneous rocks are formed by lava that cools on the Earth's surface. This lava is exposed to air and moisture and cools quickly.

Because lava is exposed to cooling air and moisture, minerals in extrusive igneous rocks form more quickly than in intrusive rocks and are much smaller than minerals in intrusive rock.

Examples: rhyolite, andesite, basalt

Igneous Rock Formation

Classifying igneous rocks

Crystal size: Rocks with large, visible crystals are “coarse-

grained rocks” (diorite) Rocks that have crystals so small we can't see

them are “fine-grained rocks” (basalt) Color:

Light (granite) Intermediate (diorite) Dark (basalt)

Homework Due Thursday 2/28

Compare and contrast intrusive and extrusive igneous rocks.

Metamorphic Rocks

Metamorphic rock forms when rock is changed by heat or pressure or both.

Q: What do you think the word 'morph' means?

Example: When granite is under pressure, the minerals inside it are flattened and form the metamorphic rock gneiss (pronounced 'nice').

Granite Gneiss

Pressure

Metamorphic Rock Formation

Pressure on rocks comes from overlying rock layers.

Heat on rocks comes from magma.

If there is enough heat and pressure, the rocks melt and magma forms, which means that the mineral grains in the rock may change in size or shape.

Classifying Metamorphic Rocks

Foliated texture means the rock has parallel bands of mineral grains caused by pressure on the original rock. Foliated rocks separate along their layers.

Non-foliated texture means that although the minerals in the rock are rearranged, they don't form visible bands. Non-foliated rocks fracture into pieces of random size and shape.

Sedimentary Rocks

Sedimentary rocks are formed from recombined sediment (sediments are small pieces of rocks and fossil broken apart by weathering and/or erosion) via either compaction or cementation.

Example: Sandstone

Classifying Sedimentary Rocks

Detrital: made of the broken fragments of other rocks (e.g. shale and sandstone)

Chemical: made of minerals that were once dissolved in water (e.g. rock salt)

Organic: made of fossils (e.g. limestone)

Exit Ticket (2/28)

What does 'morph' mean and what are two ways metamorphic rocks morph from other rock types?

What is sediment? Compare and contrast the two ways that sediments come together to form sedimentary rocks.