Rocks and Minerals Flashcards
What are the 4 characteristics that a mineral must have?
- Solid
- Naturally occurring
- Has a definite chemical composition
- On the atomic level the atoms are bound in a rigid geometric 3D arrangement (crystalline)
What is the difference between a rock and a mineral?
- Minerals have a definite chemical composition and are purely that repeating compound (Ex: Salt is all NaCl)
- Rocks are mixtures composed of grains from multiple minerals (Ex: Basalt is made of mainly of plagioclase and pyroxene minerals.)
What are 5 methods used to identify minerals?
Color, hardness, streak, luster, and cleavage
What is Mohs’ Hardness Scale? How do you use the scale to determine the hardness of a mineral?
- A scale created by Friedrich Mohs to measure mineral hardness
- You scratch a mineral against one of the members of the scale and see which one is scratched
- If it is the unknown mineral, then the mineral is softer than that particular member of the scale
- If the member of the MHS is scratched, then the unknown mineral has a greater hardness
Why are some minerals harder than others?
Mineral hardness depends on how strong the chemical bonds of the mineral are
Can you recognise a mineral with good cleavage?
Yes, different planes will usually be easy to see, some are hard to identify immediately, so it is important to look at all angles
What determines the color of a mineral?
- By what colors of light are absorbed by the mineral and which are reflected
- All but one color in a light ray gets absorbed by it, reflecting the remaining colors out to your eyes
- Ex: green mineral absorbs all colors but reflects green
What is the most abundant mineral family? Why?
Silicate minerals are the most abundant mineral family (90% of minerals) because Earth’s crust is rich in silicon.
What are the native elements?
Minerals that are made of one individual element (gold, silver, etc.).
Why is color not a good diagnostic property to determine minerals?
- One mineral could be many different colors or vary in color (ex: quartz and fluorite)
- Two very different minerals could have the same color
What is double refraction? (ex)
When you look through a translucent mineral, it will show two copies of an object, two different rays of light, creates a double image
Ex: calcite
Know the order of minerals on Moh’s Scale of Hardness.
Talc(1), gypsum(2), calcite(3), fluorite(4), apatite(5), orthoclase- feldspar(6), quartz(7), topaz(8), corundum- ruby, saphire(9), diamond(10)
2.5: Fingernail
3.5: Penny
4-5: Steel nail
5.5: Glass
6.5: Streak Plate
What is an igneous rock?
A rock that was created by the solidification (freezing) of magma
What is a sedimentary rock?
Formed by the deposition (deposited somewhere) and lithification (sediments turn into rocks) of sediments such as:
1) Fragments of preexisting rock that have been eroded and transported by water, wind, ice, and gravity
(Ex: conglomerate, sandstone, shale)
2) Remains of plants and animals
Plants buried before they decay
(Ex: coal, fossiliferous limestone)
3) Minerals that have precipitated out of salty water (usually seawater) - evaporite sedimentary rocks
Straight that leads into the Mediterranean sea seals up – salt deposits build up
What is a metamorphic rock? (ex)
Rocks formed from preexisting rocks by the application of pressure (by burial far below the surface) and/or heat (by the arrival of a nearby body of magna)
Ex: gneiss, marble, limestone, quartzite, slate
Be able to describe which one type of rock can be directly converted to another
- Metamorphic, igneous, sedimentary –> metamorphic
- All rocks can change into sediments, and then into sedimentary
- Metamorphic can be changed into igneous, but sedimentary can’t directly turn into an igneous rock
Upon what is the classification scheme for igneous rocks based?
- Texture
- Environment of Formation
- Mineral composition
- Crystal size
What is the difference between extrusive igneous rocks and intrusive igneous rocks?
Extrusive rocks are created from a volcanic eruption, where intrusive rocks are created from inside the mantle
What is the difference between lava and magma?
- Lava is magma that has been erupted out of a volcano/magma that is on the surface of the Earth
- Magma is just molten rock that hasn’t been erupted
- All lava is magma but not all magma is lava
- Not all magma gets to the surface – solidifies inside the Earth – not volcanic
Why does magma cool and solidify more slowly beneath the surface than at the surface?
It is surrounded by other hot material inside the Earth, where at the surface it is surrounded by cooler air
Why would you expect to find larger minerals in intrusive rocks than volcanic rocks?
When rocks cool inside the Earth, the temperature of mantle around the rock is warmer, giving them more time to cool. This allows for minerals to form for a longer period of time
What is the source of the heat that melts rocks deep below the Earth’s surface to form magma?
Radioactivity in the Earth’s core, leftover heat from the formation of Earth, and pressure
What causes some volcanic igneous rocks to have very low density because they are full of holes and air spaces?
The air pockets get stuck within the lava and lower the density of the mineral
What type of lava is produced by most of the volcanoes that surround the Pacific?
Intermediate igneous rocks are found at volcanic arcs, which surround the Pacific plate
What are the sources of mafic and felsic magmas (what is melted to produce these lavas)?
Mafic magma is found in the mantle, and felsic magma is found near the crust
Be able to name places around the world where you could go and collect mafic igneous rocks (or intermediate rocks).
Hawaii, there is basaltic lava, a hotspot volcano
What are the three different types of volcanoes? What are their characteristics?
1) Composite volcanoes (stratovolcanoes)
2) Cinder cones
3) Shield volcanoes
Be able to describe the process whereby sedimentary rocks are created from loose sediments (Be sure to talk about the water table and the zone of saturation).
- Water and erosion produces loose sediments, then they are deposited and buried under other sediments
- Once the sediments reach the water table, they are saturated and they are compacted and cemented until they turn into sedimentary rock
Be able to describe how the major types of sedimentary rock zones form (that is clastic, chemical, and organic sedimentary rocks).
1) Clastic sedimentary rocks form from fragments of preexisting sedimentary rock that has been transported by water, wind, or ice.
2) Chemical sediments, or evaporites, are minerals that have precipitated out of evaporating water.
3) Organic sediments formed from the remains of plants and animals.
How does coal form?
Coal is an organic sediment, formed from the remains of plants and animals building up over a long period of time
Andesite
- Extrusive
- Igneous
- Intermediate composition
- Ranges from aphanitic to porphyritic
Aphanitic
A rock with microscopic crystals in it, very fine in texture
Caldera
A large volcanic crater formed by a major eruption after the emptying of the magma chamber leading to the collapse of the mouth of the volcano