Identifying Minerals and Rocks

• Rocks are naturally occurring solid mixtures of minerals.
• Granite, an igneous rock, comprises quartz, feldspar, and mica.
• Sandstone, a sedimentary rock, is made up of quartz and feldspar.
• Marble, a metamorphic rock, consists of calcite and dolomite.
• Minerals are naturally occurring solids that are considered pure substances.
• Pure substances consist of only one type of particle and can be elements or compounds.
• Elements, like gold or silver, are minerals made of only one type of particle.
• Compounds, like quartz, sapphire, or emerald, are combinations of two or more types of particles bonded.
• Minerals are identified using lustre, hardness, transparency, streak test, cleavage or fracture, colour, and crystal formation.

Mineral Identification

• Colour is an easy but sometimes misleading way to identify minerals, since it can vary within the same mineral.
• Lustre describes the shininess of a mineral.
• The Mohs hardness scale measures a material's ability to scratch another, ranging from 1 (softest) to 10 (hardest).
• Transparency indicates how easily you can see through a mineral: transparent allows easy viewing, translucent allows partial viewing, and opaque prevents any viewing.
• Streak is the color of a mineral when scratched on a porcelain tile.
• Cleavage describes how a mineral breaks with flat surfaces and smooth edges, while fracture indicates breakage with rough surfaces and jagged edges.
• Crystal shape refers to the natural shape of a mineral in solid form.

Rock Types

• The three main categories of rocks are igneous, sedimentary, and metamorphic.
• Igneous rocks form from cooled and hardened liquid magma or lava.
• Magma is melted rock inside the Earth’s crust.
• Lava is melted rock on the Earth's surface.
• Intrusive igneous rocks, like granite, cool and harden inside the earth, allowing more time for crystal formation.
• Extrusive igneous rocks cool and harden on the Earth’s surface, resulting in less time for crystal formation.
• Igneous rocks were the first rocks on Earth, forming over 4.5 billion years ago.
• Below the earth's surface, 90% of the crust consists of igneous and metamorphic rocks.
• Sedimentary rocks are formed from compacted or cemented sediment.
• Sediment includes loose bits of broken-down rocks, minerals, and plant or animal remains like sand.
• Examples of sedimentary rocks are shale, sandstone, and conglomerate.
• Sediments pile up in layers called strata.
• Sedimentary rocks form through compaction from the weight and pressure of sediment layers.

Sedimentary Rock Formation

• Cementation occurs when sediments are glued together by another material to form sedimentary rock.
• Weathering creates sediment, while erosion transports it.
• Weathering breaks down rocks and minerals into smaller pieces called sediments.
• Mechanical weathering involves physical forces like gravity, water, wind, heat, and cold.
• Chemical weathering involves chemical reactions such as rusting or dissolving minerals in water.
• Biological weathering occurs when living things break down rocks or minerals mechanically or chemically.
• Erosion is the movement of sediments from one place to another by gravity, wind, or water.
• Sedimentary rocks form when sediments are compacted and cemented together.
• Weathering forms sediments, erosion transports sediments, and sediments are deposited in layers or strata.
• Sedimentary rocks are the most likely place to find fossils, comprising about 75% of the rocks on Earth's surface.
• Metamorphic rocks form when intense heat and pressure deep inside the Earth transform one rock type into another.
• Parent rock looks different from its newly formed metamorphic version.
• For example, the igneous rock granite becomes gneiss, and the sedimentary rock shale becomes slate.
• The metamorphic version of slate is schist
• Metamorphic rocks are typically formed deep underground and are not often exposed above ground.
• The rock cycle describes the natural process of rocks changing form over long periods.

Earth Layers and Observations

• Direct observations involve scientists physically visiting a site or taking samples.
• Indirect observations allow scientists to make inferences without being physically present or taking samples.
• The layers of the Earth, from outside to inside, are the oceanic crust, continental crust, upper mantle, lower mantle, outer core, and inner core.
• The crust, the Earth's outer layer, is made of solid rock and is divided into oceanic and continental crust.
• Continental crust is thicker (35-70 km) and less dense.
• Oceanic crust is thinner (5-10 km) but denser.
• Much of Earth’s crust is covered by water.
• The deepest hole on Earth extends 12 km into the continental crust.
• The mantle is the layer between the crust and the outer core, made of partially melted rock.
• Convection currents in the mantle are thought to move the crust.
• The mantle is the Earth’s largest layer by mass and volume, with an average temperature of 1000°C.
• The core, the Earth's inner part, has two main parts: the outer core and the inner core.
• The outer core is a liquid layer of iron and nickel with an average temperature of around 5000°C.
• Convection currents in the outer core are thought to create Earth's magnetic field.
• The inner core is a solid ball of iron and nickel.
• The inner core has an average temperature of around 5500°C, but remains solid due to immense pressure.