Rocks and minerals
What are rocks and minerals?
How are they formed?
What are the different types of rocks and minerals?
A rock is any naturally occurring and coherent solid mass or aggregate of minerals or mineraloid matter.
Naturally occuing means that they may be made by animals (pearls or ivory), but not by humans.
Coherent means that it is united and consistent.
Aggregate of minerals or mineraloid matter means that rocks are made up of smaller substances called minerals.
Rocks are usually categorized by the minerals in them, their chemical composition, or the way in which they are formed.
Rocks are usually grouped into three main groups: igneous rocks, metamorphic rocks and sedimentary rocks based on how they are made.
Minerals are naturally occurring, homogeneous, inorganic solids having a characteristic chemical composition and crystalline structure.
There are lots of minerals. We will look at some of the more important ones in this unit.
Homogeneous means that the minerals are uniform and all alike within.
Inorganic means that they are not produced by living things (ivory, pearls, petrified trees, amber, etc.)
A characteristic chemical composition and crystalline structure means that the chemicals inside them bind in predictable and dependable ways forming a crystal structure.
Let's look more closely at some of the more common rocks and minerals.
We'll begin with rocks based on how they are formed:
Igneous - created by cooling of molten rock
Sedimentary - created by cementation of small sediments of rock
Metamorphic - created by partial melting and squishing due to intense heat and pressure
As you can see from this, the same materials on Earth's surface keep getting recycled and change forms. The Earth is dynamic (ever changing).
Let's begin with the first rocks...igneous:
There are two types of magma, so there are two types of igneous rocks...Mafic (dark and heavy) and Felsic (light).
Also, these rocks could be cooled slowly underground and get big crystals or erupt and form so quickly that they have tiny crystals:
Know Granite, Pumice, Gabbro, Basalt, Scoria, and Obsidion
Now let's look at sedimentary rocks:
These rocks are cemented from sediments of other rocks. They are defined by what sediment makes up the rock. Sand sediment makes sandstone...salt makes halite...clay makes shale...etc.
These rocks are made gently and preserve footprints and fossils best.
Know shale, sandstone, conglomerate, limestone, halite. Coal and gypsum are also to be known, but coal is usually considered metamorphic and gypsum a pure mineral.
Now let's look at metamorphic rocks:
These are created by adding significant heat and pressure to other rocks. They are characterized by what rock they started as as well as how much of their minerals melted and reformed.
Know slate, schist, gneiss, marble, and coal.
Let's look closer at some of the minerals making up those rocks:
These minerals may be sorted and organized in myriad ways (hardness, cleavage, shape, color, properties, etc.)
Know sulfur, biotite, muscovite, magnetite, agate, turquoise, azurite, malachite, hematite, talc, gypsum, calcite, flourite, feldspar, quartz, amethyst, rose quartz, smoky quartz, olivine, galena, topaz, garnet, corundum, iron pyrite, graphite, diamond, jade, copper.
Are you ready for the test?
Define rock, mineral, and ore.
How would you tell is an igneous rock were mafic, felsic, intrusive, or extrusive?
What does the texture tell us about the rock's formation?
Which type of rock would you most likely find fossils in?
What causes metamorphism?
Describe the effects of metamorphism.
Draw the rock cycle.
Granite, Salt and pepper appearance, light in color, large grain size
Pumice, Light in color, full of holes, floats in water, tiny grain size
Gabbro, Dark in color, large grain size
Basalt, Dark in color, tiny grain size
Scoria, Dark in color, full of holes, tiny grain size
Obsidian, Black, glassy, conchoidal fracture (sharp, circular breaks), tiny grains
shale, Layers of clay
sandstone, Sand cemented together, sometimes layered, bite sand
conglomerate, Mix of grain sizes cemented together
limestone, Light in color, bubbles with acid
halite, Clear, rectangles, salty
slate, Hard, shiny layers of clay (some metamorphism)
schist, Shiny rock (metamorphism pulled out the mica)
gneiss, Mangled layers / bands
marble, Hard, shiny, light in color, bubbles in acid
coal, Black, lightweight, streaks black, burns easily
sulfur, Yellow, burns blue
biotite, Thin, flat, dark layers
muscovite, Thin, flat, light layers
magnetite, usually heavy and dark, always magnetic
agate, Tiger eye moving light patch
turquoise, Light blue
azurite, Blue rock
malachite, Green rock
hematite, May be polished silver or natural red, always streaks red
talc, Soft enough to rub off the powdered rock with finger
gypsum, White and soft (fingernail will scratch it)
calcite, Clear, squished square, doubles images
fluorite, Translucent and green
feldspar, Pink and edgy
quartz, Clear and translucent, hard
amethyst, Purple quartz
rose quartz, Pink quartz
smoky quartz, Grey quartz
olivine, Olive green rock
galena, Silver and cubical, smells like sulfur with acid
topaz, Translucent brown, very hard
garnet, Dark red, edgy
corundum, Extremely hard, ruby and sapphire
iron pyrite, Gold in color, squared, hard
graphite, Grey and streaks grey very easily
diamond, Clear, refractory, hardest
jade, Milky green
copper, Green or brown, metallic
Flint, Easily broken