Lab 5

Lab 5: Sedimentary Rocks Part A: Sedimentary Rocks Identification (2pts per rock, total: 24 points) Complete the following table with information about each of the 12 samples in the lab. Sample ID Identifying Characteristics (minerals, grain sizes, etc.) Texture Rock Name 1 Fizzes readily with dilute acid. Chemical crystalline Oolitic Limestone 2 Small visible grains, no rock or shell fragments, strong pink hue Clastic coarse-grained Quartz Sandstone 13 Microscopic grains, smooth with conoidal fractures, no rock or shell fragments Chemical micro- crystalline Chert 28 Visible grains, rough texture, rock fragments imbedded in the rock Clastic coarse-grained Arkosic Sandstone 30 Microscopic grains, smooth with a conoidal fractures on one side, no shell or rock fragments Clastic fine-grained Mudstone 37 Microscopic grains, smooth with fissile fractures, no rock or shell fragments Clastic fine-grained Shale 72 Microscopic grains, no rock or shell fragments, would burn and is biological in nature Biological Coal 101 Visible grains, rough texture, rock fragments imbedded in the rock Clastic coarse-grained Conglomerate 104 Microscopic grains, smooth, no rock or shell fragments, no rock or shell fragments Clastic fine-grained Mudstone 105 Fizzes readily with dilute acid. Chemical crystalline Fossiliferous Limestone IDS-10 Small visible grains, no rock or shell fragments, gritty feel Clastic coarse-grained Graywacke IDS-23 Fizzes with dilute acid, when the rock has been powdered. Chemical crystalline Dolostone Manlius Fm Fizzes readily with dilute acid. Chemical micro- crystalline Micritic Limestone 1

Part B: Questions (total 26 pts.) 1a) Summarize the similarities and differences between quartz sandstone, arkosic sandstone, and graywacke sandstone. (3 pts) All of these samples contain sand, but arkosic sandstone contains larger grains while graywacke and quartz sandstone both contain smaller grains giving them a gritty feel. Graywacke and quartz sandstone can be differentiated by their color as quartz sandstone has a pinkish-red hue while graywacke is white. 1b) Greywacke sandstone can sometimes be confused with mudstone. Both have mud, but what makes greywacke different? How can you tell these two rock types apart? (2 pts) Greywacke has a gritty texture with visible grains while mudstone is smooth with microscopic grains. 1c) Shale is mudstone but mudstone is not necessarily shale, what makes shale different from other mudstones? ( 2 pts. ) Both are made of ancient mud, but mudstone breaks into blocky pieces while shale breaks into thin sheets. 1d) What is the visual difference between the micritic, fossiliferous, and oolitic limestones? (3 pts) Micritic limestone is crystalline which means grains are microscopic, oolitic limestone has small visible grains and has a gritty feel, and fossiliferous limestone contains indentations of fossilized organisms. 1e) What rock might you confuse oolitic limestone with and how could you tell the difference between them? (2 pts) You might confuse graywacke and oolitic limestone. You would have to expose each rock to dilute acid to tell the difference. The rock which fizzes at the acid would be the oolitic limestone while the rock that does not will be the graywacke. 1f) How can you tell the difference between limestone and dolostone? ( 2 pts. ) To tell the difference between limestone and dolostone, you need to expose the rocks to dilute acid. The rock that fizzes readily with the acid is limestone. The rock that does not fizz readily with the acid and must be powdered for it to fizz is dolostone. 1g) Both chert and micritic limestone are going to be microcrystalline materials. What two features would help you tell them apart from one another? (2 pts) Firstly, micritic limestone fractures differently than chert. Chert produces sharp conchoidal fractures when it breaks while micritic limestone does not. Limestone also fizzes when exposed to acid while chert does not. 2