Mineral and Rock Identification Lab

Part 1: Mineral and Rock Identification 

Minerals 

	Mineral	Luster	color	Hardness (Mohrs)	Cleavage and fracture	Streak	Special characteristic
1	Fluorite	Vitreous	Pale green	4	Rounded streak	white	Fluorescent
2	Feldspar	Vitreous. Pearly on some cleavage faces	White grey	6	Perfect in two directions	white	Igneous rock
3	Hematite	Black to steel-grey	Dark grey	5	None	Red to reddish brown	Magnetic when heated
4	Pyrite	Metallic color	Brass yellow	6	Breaks with a conchoidal fracture	Brass yellow	Brittle and flaky
5	Milky Quartz	Vitreous	Milky	7	Conchoidal	None	Dissolves in acid
6	Calcite	Vitreous	White, colorless	3	Perfect, rhombohedral	White	Bubbles in acid
7	Mica-Muscovite	Pearly to vitreous	Thick specimens: brown  Thin: colorless	2.5	Perfect	White	Rock-forming mineral
8	Magnetite	Metallic to submetallic	Black to silver grey	5	None	Black	Magnetic
9	Gypsum-alabaster	Pearly	Clear, colourless, white	2	Flat sheet-like	White	Sedimentary rock
10	Talc	Pearly	Green, white, brown	1	Perfect	White	Very soft and waxy
11	Halite	Vitreous	Colorless, white	2.5	Perfect, cubic	White	A natural salt
12	Mica-Biotite	Vitreous	Black, dark green	2.5	Basal, perfect	White to grey, flakes produced	A rock-forming mineral
13	Graphite	Metallic, earthy	Steel gray to black	1	Perfect in one direction	Black	Smudges on hand
14	Gypsum-Satin Spar	Vitreous	Clear, colorless, white	2	Perfect	White	fibrous
15	Gypsum-Selenite	Vitreous	Clear	2	sheet	White	Mica-like

Rocks 

	Rocks	Color	texture	Hardness	Composition	Grains/crystal
1	Obsidian	Black or blackish green	Fine-grained	5	Felsic, SiO 2	None because it is Amorphous
2	Granite	white	Porphyritic texture	7	Quartz and feldspar	coarse
3	Basalt	grey	Fine Grain	6	Similar to gabbro	Fine Grains
4	Pumice	Beige or grey		6	Feldspar, augite, hornblende, and zircon	Very fine-grained
5	Rhyolite	Dark grey		6	Quartz, plagioclase, sanidinde,	Fine-grained
6	Shale	Earthy tones	Clastic (fragmental)	3	Mostly quartz, feldspar and clay minerals	Less than 0.0004 cm
7	Calcareous Tufa	Brown	Chalky texture	2.5	Calcium carbonate	Fine-grained, soft, and porous
8	Sandstone	Pink and red	Clastic (fragmental)	6-7	Mostly quartz, feldspar and clay minerals	0.2 t 0.006cm
9	Conglomerate	Earthy colors	Clastic (fragmental)	3	Mostly quartz, feldspar and clay minerals	Pebbles, cobbles embedded in sand
10	Limestone	Earth stones	Bio-clastic	3	Calcium carbonate	Microscopic to course
11	Slate	grey	Fine texture	3	Fine, microscopic clay or mica	Fine-grained
12	Marble	white	Finely crystalline to medium or coarse texture.	2.5	Calcite, or dolomite	Fine-coarse
13	Quartzite	white	Crystalline texture	6	Quartz grains fuse, Sandstones	Fine to coarse
14	Gneiss	Brown, white	Crystalline texture	7	Light colored quartz and feldspar	Coarse-grained
15	Schist	grey	Schistose texture	4	Chloride, biotite, muscovite	Coarse-grained

Answer the following questions: 

Explain the rock cycle. 

This is the process in which rocks are continuously transformed from one type of rock to another. The three types of rocks include igneous rocks, sedimentary rocks, and metamorphic rocks. These three types of rocks transform, and the changes they undergo is what constitutes the rock cycle. Beneath the earth surface, rocks occur in the forms of magma. When the magma cools and crystallizes, it forms igneous rocks. Intrusive igneous rocks are brought to the surface through weathering resulting in the deposition of igneous sediments. These sediments are then compacted through the lithification process resulting in sedimentary rocks. The sedimentary rocks formed end up being buried back into the earth crust where the temperatures, as well as the pressure, are high. This results in the formation of metamorphic rocks. Because of the excess temperature and pressure, the rocks melts again creating magma making the cycle start again. 

What did you find the most useful property to identify your minerals? 

The most useful characteristics I found significant when identifying the minerals include the unique components of the mineral, like the taste, their magnetism, crystalline structure, as well as, their reaction with acids. 

What was different about the components of your conglomerate and granite? 

The fundamental difference between them is the texture. Granite is made up fair coarse grains while conglomerate is very coarse since it is made up large pieces of gravel. Gravel is an igneous rock while conglomerate is a sedimentary rock. 

What was similar between your limestone and marble? 

Marble is made of limestone. Thus, both of them are composed of calcite. Also, both of the two rocks react to acids. 

What was different between your sandstone and quartzite? 

Sandstone is a sedimentary rock while quartzite is a metamorphic rock. Also, sandstone is a make of sand, and its grain size is medium while quartzite is course material and composed of quartz and sandstone. 

Describe the differences between the conglomerate, sandstone, and shale. 

The fundamental difference between conglomerate, sandstone, and shale is on the texture and grain size of the rocks. The conglomerate is very course and is composed of visible pieces of rounded gravel. Sandstone is made up of sand particles which are medium in size and is slightly smoother. Lastly, shale is composed of very fine particles of sand and are very smooth. 

What is similar and what is different about your granite and gneiss? 

One of the similarities between granite and gneiss is that they are both course materials with two distinct minerals. However, granite is a metamorphic rock while gneiss is an igneous rock. 

Part 2: Geologic time 

Relative dating methods: 

Using the diagram below, and the rules of relative dating, answer the following questions. 

Which unit was being deposited when the fault happened? 

Unit 10 was being deposited when the fault happened since it filled more on the right compared to how it filled on the left. 

Explain why the funny line between units 3 and 4 is a disconformity and not an angular unconformity. 

The funny line between unit 3 and 4 is not an angular disconformity. This is because other units would have been closer to unit 4 if it were an angular unconformity. However, there is a period that is missing in which erosion rather than deposition took place between units 3 and 4, indicating a disconformity. 

Hypothetically, if the trees and ground at the top were covered by the ocean, and deposition resumed, what type of unconformity would be above unit 12, and why? 

Since there is no deposition taking place, an unconformity would result. This results in the formation of a gap between that layer and the next. 

Would unit 11 likely to be present when the fault happened? Why or why not? 

No. As per the principle of crosscutting, unit 11 ought to have been affected by the fault if it was older than the fault. The fact that it was unaffected is a clear indication that it is younger. 

Explain why units 1-5 were not deposited in this position 

According to the principle of horizontality, sediments are generally deposited horizontally unless they are disturbed. Initially, the layers were horizontal until they were folded. 

In some areas, faults are known to act as a petroleum trap. If unit 2 has oil, and unit 3 is shale, what part of unit 2 would you drill into, above or below the fault, and why? 

The drilling ought to be done below the fault because the oil and gas. This is because the oil and gas well would dry up fast if the drilling is done above the fault. 

Radiometric dating 

Answer the following questions 

In order to ascertain useful dates on rock units to help determine the age of major events. Your mission is to date what is thought to be a very old fossil with a volcanic ash layer immediately above the fossil. We do know the fossil is at least more than 300 million years old. Should we use carbon 14 to date the fossil, or uranium 238 to date the volcanic ash layer, and why? 

Since the age of the fossil is more 300 million, it won’t be possible to find its age using carbon-14. This is because the half-life of carbon is 15730 years, thus, making it impossible to data a 300 million years old fossil. Uranium 238 has a half-life of 4.5 billion years. However, it can’t be used to date fossils because fossils do not contain uranium. Uranium 238 is only used to date volcanic rocks of very old age. Thus, neither carbon-14 nor uranium 238 can be used to date the fossil. 

We find samples of an igneous rock demonstrate it has been through 3 half-lives. The test element has a half-life of 300 million years. How old is the rock? 

If the parent isotope starts with 100 grams, but your samples yield only 6.25 grams of the parent isotope, how many half-lives have passed? 

Therefore, the isotope has passed four half-lives. 

What would unstable isotope be best to refine the date of bones found in a cave hearth built by humans between 20,000 and 40,000 years ago? 

The unstable isotope that is commonly used Carbon-14. It has a half-life of 5730 years and can be used to measure fossils of up to 50,000 years. Thus, carbon 14 can best refine the date of the bones found in the cave built between 20,000 and 40,000 years. 

Argue with the following: A stone tool fashioned from a chunk of obsidian yields a date of 3,000,000 years old, therefore, the tool was made by a human 3,000,000 years ago. 

Just because the chunk of the obsidian yields 3,000,000-year-old doesn’t mean that the tool was made by humans 3,000,000 years, the origin of humanity is traced back to 2 million years ago. Thus, it doesn’t make sense that the tool was created by humans 3 million years ago — instead, the obsidian on the tool the age of the mineral when it was formed from crystallization of magma.