Identifying Granitoids and Other Granite Rocks

Granite rock has become so common in homes and buildings that anyone these days can name it when they see it in the field. But what most people would call granite, geologists prefer to call granitoid until they can get it into the laboratory. Thats because relatively few granite rocks out there are truly petrologically granite. How does a geologist make sense of granitoids? Heres a simplified explanation. The Granitoid Criterion A granitoid meets two criteria: (1) it is a plutonic rock that (2) has between 20 percent and 60 percent quartz. Plutonic rocks cooled at depth very slowly from a hot, fluid state. A sure sign is well-developed, visible grains of various minerals mixed in a random pattern  as if they had been baked in a pan in the oven. They look clean, and they dont have strong layers or strings of minerals like those in sedimentary and metamorphic rocks.​As for the quartz, a rock with less quartz than 20 percent is called something else, and a rock with more than 60 percent quartz is called quartz-rich granitoid (a remarkably simple answer in igneous petrology). Geologists can assess both of these criteria (plutonic, abundant quartz) with a moments inspection. The Feldspar Continuum OK, we have abundant quartz. Next, the geologist evaluates the feldspar minerals. Feldspar is always present in plutonic rocks whenever theres quartz. Thats because feldspar always forms before quartz. Feldspar is mainly silica (silicon oxide), but it also includes aluminum, calcium, sodium, and potassium. Quartz—pure silica—wont start forming until one of those feldspar ingredients runs out. There are two types of feldspar: alkali feldspar and plagioclase. The balance of the two feldspars is the key to sorting out the granitoids into five named classes: Granitoid with only (90%) alkali feldspar is alkali-feldspar graniteGranitoid with mostly (at least 65%) alkali feldspar is syenograniteGranitoid with a rough balance of both feldspars is monzograniteGranitoid with mostly (at least 65%) plagioclase is granodioriteGranitoid with only (90%) plagioclase is tonalite True granite corresponds to the first three classes. Petrologists call them by their long names, but they also call them all granite. The other two granitoid classes arent granites, although granodiorite and tonalite in certain cases can be called a name very much like granite (see the next section). If you have followed all this, then you will readily understand the QAP diagram that shows it graphically. And you can study the gallery of granite pictures and assign at least some of them exact names. The Felsic Dimension OK, weve dealt with the quartz and the feldspars. Granitoids also have dark minerals, sometimes quite a lot and sometimes hardly any. Usually, feldspar-plus-quartz dominates, and geologists call granitoids felsic rocks in recognition of this. A true granite can be rather dark, but if you ignore the dark minerals and assess only the felsic component, it can still be properly classified. Granites may be especially light-colored and nearly pure feldspar-plus-quartz—that is, they may be very highly felsic. That qualifies them for the prefix leuco, meaning light-colored. Leucogranites may also be given the special name aplite, and leuco alkali feldspar granite is called alaskite. Leuco granodiorite and leuco tonalite are called plagiogranite (making them honorary granites). The Mafic Correlative Dark minerals in granitoids are rich in magnesium and iron, which dont fit in felsic minerals and are called the mafic (MAY-fic or MAFF-ic) component. An especially mafic granitoid may have the prefix mela, meaning dark-colored. The most common dark minerals in granitoids are hornblende and biotite. But in some rocks pyroxene, which is even more mafic, appears instead. This is unusual enough that some pyroxene granitoids have their own names: Pyroxene granites are called charnockite, and pyroxene monzogranite is mangerite. Still more mafic a mineral is olivine. Normally olivine and quartz never appear together, but in exceptionally sodium-rich granite the iron-bearing variety of olivine, fayalite, is compatible. The granite of Pikes Peak in Colorado is an example of such a fayalite granite. A granite can never be too light, but it can be too dark. What stone dealers call black granite is not a granite at all  Ã¢â‚¬â€¹because it has little or no quartz in it. Its not even a granitoid (although it is a true commercial granite). Its usually gabbro, but thats a subject for another day.

How Chris Kyle Was The Most Lethal Sniper During American...

It is one thing to initiate change and think of ethics within your unit using the principles and concepts from this course. It is a whole other experience to initiate any of these practices during combat operations out of necessity to save lives. Chris Kyle was a U.S. Navy Seal sniper during the battle of Rhamadi in 2006. Chris is known as the most lethal sniper in American history and for his autobiography American Sniper. The website visionary leader.org says that â€Å"visionary leaders require core values, clear vision, empowering relationships and innovative action†. Chris Kyle displayed these characteristics throughout his career. However, his most notable display of these individualities came while performing combat operations in†¦show more content†¦Sniper over-watch is a task where a sniper takes an elevated position to protect advancing troops with intelligence on their surroundings and lethal fire if necessary. During these over-watch missions, Chris discovered that the Marines were not proficient with the necessary skills for this type of battle. This became painfully evident to him by the number of Marines he witnessed through the lens of his sniper scope being carried away by their friends. At that moment, his new mission was whatever was necessary to save Marines. Chris had specialized training in this type of warfare being waged and knew that he could train these guys to endure. According to the Thomas N. Barnes Center, Change Management (pg 17) change is about survival and Chris wanted them to survive. He had built a rapport with these Marines over the course of a few months. That rapport set the stage for his plan. He spoke with the Marine platoon sergeant to gain permission to train his men. Promptly after that conversation Chris started a training regime that taught them everything they needed to know about asymmetric warfare, Navy Seal style of course. After he completed his training regime, his vision was soon to become a reality. He proceeded to build teams who now possessed necessary skills in asymmetric warfare and he motivated and inspired and gave them goals to attain. He then empowered them and

Recycling Myths Speech Essay Example For Students

Recycling Myths Speech Essay Jamie Klein 2/7/05 S121 Thesis: There are many myths about recycling. INTRO: Attn Gttr:Most people in here probably recycle on some level; some more than others. And probably, most people in here assume that they are saving natural resources and helping the environment. However, this is not always true. Thesis:There are many myths about recycling. Preview: Today in my speech, I will give you facts that may surprise you and that youve probably never heard about landfills, natural resources, and energy conservation. Transition:Everyone has seen or heard people saying that we are running out of landfill space and that they are polluting our environment. BODY: I.This statement is not true. a.Firstly, we are not in danger of running out of landfill space. According to Jay Lehr PhD, in the April issue of public policy magazine, Intellectual Ammunition, all the garbage we will generate in the next 10 centuries will require less than 35 square miles to a height of only 300 feet. Also, according to Daniel Benjamin of PERC Reports, the United States has more landfill space then ever before. b.Another myth about landfills is that they are poisoning the soil and our water supply. Even the EPA, the Environmental Protection Agency, says modern landfills pose little to no risk to humans. Modern landfills are built on a thick foundation of clay and plastic liners. Also, the methane gas produced in biodegradation is often times purified and sold Transition:Now, lets talk about some of the objects that go into those landfills. II.Paper, glass, and plastic are the three main recyclable goods. a.Weve all been at the library or at home and printed a website off the computer and didnt realize it was going to use 50 sheets of paper and then felt guilty because weve always been told not to waste paper because were running out of trees. Quoting Mr. Lehr again, we are not cutting down endangered forests today to make paper. We plant far more trees than we harvest each year. Wood is in ample supply. b.Glass is another resource we dont have to worry about, since its made from silica dioxide, which is just beach sand, the most abundant mineral on earth. c. Plastics are petroleum based byproducts, which is limited. However, new technology allows use to make plastics from plants through fermentation. Transition:The last myth I want to touch on is energy conservation. III.A frequent pro-recycling argument is that manufacturing products from scratch rather than from recycled goods wastes energy. a. It is actually just the opposite. Making products from recycled goods uses more energy and water and produces the same or more air pollution. As stated by Recycling Today Online in January 2001, recycling uses more energy and financial resources to sufficiently clean material to meet quality and safety specifications. Conclusion:I hope this speech has cleared up some fallacies weve all been taught about landfills, natural resources and energy consumption. Final Comment: So, the next time you go to throw your newspaper in the recycling bin, think about where its headed. WORKS CITED Lehr, J. (2003). Recycling: Your Time Can Be Better Spent. Retrieved February 6, 2005, from The Heartland Institute Web site: http://www.heartland.org/PrinterFriendly.cfm?theType=artId;th eID=11735 Benjamin, D. (2003). Eight Great Myths about Waste Disposal. Retrieved February 6, 2005, from PERC Web site:http://www.perc.org/publications/percreports/sept2003/ recycleing.php?s=2 Archer, Joan. (2001). Recycled PET: Should it be Used in Making New Bottles? Retrieved February 9, 2005, from Recycling Today Online Web site: http://www.recyclingtoday.com/articles/article.asp?Id=403;SubC atID=16;CatID=6 About The Heartland Institute: http://www.heartland. org/Article.cfm?artId=10582 .