Lab_GEOL111_Rocks1 Ig and Sed

Geology 111: Lab: Rocks Part 1. Name: _______Anya Donders____________________ Lab Partner(s): ______________________ Lab Instructor: ______________________ Lab Day (Circle One): M T W R F M

Fig. 1. Estimating mafic and felsic minerals.

s s mafic, etc.) environmen t A 30 70 intermediat e Oceanic and continental B 10 90 felsic Continental C 10 90 felsic Continental D 85 15 felsic Continental Part 2. Differences between the same type of rocks. Here, we are going to look at three samples of granite. You’ll note many of these rocks are polished- these are countertop samples that stores discard and allow folks to come pick up for free. You can think of this as a geologists’ Christmas. We use these for teaching, decoration, just about everything- for example, all of my kitchen trivets are just discarded countertop pieces. The polished samples help us see the minerals a bit better when we’re first learning, so that’s why they make great teaching tools! First, list the minerals in each and describe them- how did you identify them and are the general percentages of each? Then, use your understanding of Bowen’s reaction series to discuss how their formation differed from one another! Use specific minerals and (relatively specific) temperatures, as well as specific discussion of crystal sizes. Smaller sample (“golden brown granite”) is A, Larger sample (“Kim Meyers’ kitchen”) is B. Non-countertop sample is C. B: 15% (mostly felsic) light mineral, igneous rocks. C: 50% intermediate the cooling rate was quick and there was 2 cooling cycles because crystals aren’t that large and there are different grain sizes filing the cracks A: 30% (felsic) There is a lot of potassium vs sample B because it Is pink. Part2. Identifying rocks by features.

Name the specimens in your igneous rock set by following the steps below for each specimen using provided resources. You should have a hand lens (a small magnifying tool, essential for all geologists) to help you view the minerals- it is a needed resource! Remember to think of the minerals you learned last week to guide you here! Step 1: Determine the color and proportion of minerals. Use this to determine whether the rock is Felsic, Intermediate, Mafic, or Ultramafic, and enter it into the table below in the Rock Type column. Step 2: Determine the Grain Size and textures (i.e., aphanitic, phaneritic) of each rock sample. Step 3 : Use the Rock Type and Grain Size to determine the Rock Name . Step 4: Note features that may help you determine the rock. Step 5: Determine if the rock is Intrusive or Extrusive . Possible rock options: Andesite Basalt Diorite Granite Gabbro Granite Obsidian Pumice Rhyolite Peridotite

Specimen Minerals present Mineral Composition (%) Rock type (felsic, etc) Grain size and textures present Notable features? (vesicles, est. density, etc.) Rock Name Intrusive or Extrusive? 2H quartz 90% felsic and 10% mafic felsic Small grain size Vesicles, light weight pumice Extrusive 2C Feldspar and quartz 85% felsic and 15% mafic felsic Large grain sizes pink Granite Intrusive 2E Olivine 95% mafic 5% felsic Mafic Small grain size vesicles basalt Extrusive 2J Pyroxene 85% mafic 15% felsic Mafic microscopic small grain size Shiny Obsidian Extrusive 2G Feldspar and quartz 90% felsic and 10% mafic Felsic Very large grain size Pink streaked crystals Rhyolite Intrusive 2I Pyroxene 85% mafic and 15% felsic mafic Large grain size Clusters of crystals and dense Andesite Intrusive 2B pyroxene 85% mafic 15% felsic Mafic Small grain sizes Dense gabbro Extrusive 2X Plagioclase 70% felsic and 30% mafic Intermediate Large grain sizes Shiny crystals Diorite Intrusive 2T olivine 95% mafic 5% felsic Ultramafic Small grain sizes Very large peridotite Intrusive 2D Feldspar and quartz 85% felsic and 5% mafic Felsic Small grain sizes pink Granite Intrusive

Sedimentary Rocks: Identifying sorting and roundness and grain size: Part 1. Gigapan images. First, you’ll use excellent gigapan images. The names of the sediments might be in the title, but that’s not what you need to answer this question! You’ll need to analyze these thoroughly. 1. Look at this sediment sample ( http://gigapan.com/gigapans/176844 ). In detail, discuss its sorting and rounding using the terms you’ve used in lecture and lab. How mature is this rock? Then, hypothesize what type of environment this sediment was found in- back up your reasoning using the evidence you found on its sorting and rounding. Note: there’s no measurement tool, so you can’t interpret grain size. This rock isn’t very mature because it’s not well sorted and there are large and small sediments combined. This could have been found in a river because they are rounded and smooth which would mean there was lots of movement against other rocks. 2. Look at this sediment sample ( http://gigapan.com/gigapans/168572 ). In full detail, discuss its maturity (or lack thereof-both textural and chemical). What variables are contributing to your decision? Make sure to be explicit (including length of transport, rounding, sorting, minerals present, etc.). Then, hypothesize what type of environment this sediment was found in- back up your reasoning using the evidence you found on its sorting and rounding. Note: there’s no measurement tool, so you can’t interpret grain size. This sediment is well sorted and very mature because the grain sizes are all around the same and pretty fine. The sediments are somewhat rounded and appear smooth.

Using the provided samples and resources, identify their properties and rock name. Then provide a brief description of where it may have formed and the evidence to back up your answer. Available Rocks: Arkose Sandstone Breccia Coal Conglomerate Coquina Limestone Quartz Sandstone Claystone/shale Chalk Travertine Siltstone Chert Specimen Texture (Grain Size, Shape, Sorting) or other features Type (Clastic, Chemical, or Biogenic) Minerals/Rock Fragments Present (%) Rock Name Rock History (Transport distance, maturity, environment, etc. Not all will be relevant for all rocks) 1J Small grain size And well sorted shale with large fossils Clastic 20% fossils 80% shale grains Shale Somewhat mature, by water, weathered 1C Poorly sorted and large grain size clastic 75% shell material (calcite composition) 25% Felsic material Coquina Not mature 1X Small grain size and very well sorted, layering Clastic 30% lighter colored felsic, 70% red material (maybe iron rich and mafic) arkose sandstone Mature because the edges are rounded from weathering, transported for a while because of sorting, probably found at desert or beach 1Q Very small grain size, well sorted, smooth chemical 10% mafic materials and 90% felsic material (quartz ad/or Chert Not mature

silicates) 1T Small grain size Clastic 95% felsic 5% mafic Quartz sandstone Somewhat mature it has weathering edges not transported far because of angular edges. Maybe formed at a be 1A White color, well sorted Clastic made from biogenic materials 100% felsic chalk Very mature 1W Small grain size and well sorted Clastic Clastic 70% mafic and 30% felsic Siltstone Probably from water, somewhat mature, maybe transported far because of grain size 1I Smooth with sharp edges, large and small grain sizes, poorly sorted, dark grains throughout Clastic 70% materials and grains 30% mafic grains Breccia Angular with sharp edges, so was probably not transported far and not very mature 1E Light color, heavy with many holes, angular Clastic 80% felsic and 20% mafic Travertine Somewhat mature because its angular but not sharp. Probably found near a hot spring 1G Black color, well sorted Biogenic 95% carbon composite and 5% other materials Coal Mature