Learn About the Many Varieties of Quartz

Learn About the Many Varieties of Quartz Quartz  is an old German word that originally meant something like hard or tough. It is the most common mineral in the continental crust, and the one with the simplest chemical formula: silicon dioxide or SiO2. Quartz is so common in crustal rocks that its more notable when quartz is missing than when its present.   How to Identify Quartz Quartz comes in many colors and shapes. Once you start studying minerals, though, quartz becomes easy to tell at a glance. You can recognize it by these identifiers: A glassy lusterHardness 7 on the Mohs scale, scratching ordinary glass and all types of steelIt breaks into curved shards rather than flat-faced cleavage fragments, meaning it exhibits conchoidal fracture.Almost always clear or whiteAlmost always present in light-colored rocks and in sandstonesIf found in crystals, quartz always has a hexagonal cross-section like that of a common pencil. Most examples of quartz are clear, frosted, or found as milky-white grains of small size that dont display crystal faces. Clear quartz may appear dark if its in a rock with a lot of dark minerals. Special Quartz Varieties The pretty crystals and vivid colors youll see in jewelry and in rock shops are scarce. Here are some of those precious varieties: Clear, colorless quartz is called rock crystal.Translucent white quartz is called milky quartz.Milky pink quartz is called rose quartz. Its color is thought to be due to various impurities (titanium, iron, manganese) or microscopic inclusions of other minerals.Purple quartz is called amethyst. Its color is due to holes of missing electrons in the crystal in combination with iron impurities.Yellow quartz is called citrine. Its color is due to iron impurities.Green quartz is called praseolite. Iron impurities account for its color, too.Gray quartz is called smoky quartz. Its color is due to holes of missing electrons in combination with aluminum impurities.Brown smoky quartz is called cairngorm and black smoky quartz is called morion.The Herkimer diamond is a form of natural quartz crystal with two pointed ends. Quartz also occurs in a microcrystalline form called chalcedony. Together, both minerals are also referred to as silica. Where Quartz Is Found Quartz is perhaps the most common mineral on our planet. In fact, one test of a meteorite (if you think youve found one)  is to be sure it doesnt have any quartz. Quartz is found in most geologic settings, but it most typically forms sedimentary rocks like sandstone. This is no surprise when you consider that nearly all the sand on Earth is made almost exclusively from grains of quartz. Under mild heat and pressure conditions, geodes can form in sedimentary rocks that are lined with crusts of quartz crystals deposited from underground fluids. In igneous rocks, quartz is the defining mineral of granite. When granitic rocks crystallize deep underground, quartz is generally the last mineral to form and usually has no room to form crystals. But in pegmatites quartz can sometimes form very large crystals, as long as a meter. Crystals also occur in veins associated with hydrothermal (super-heated water) activity in the shallow crust. In metamorphic rocks such as gneiss, quartz becomes concentrated in bands and veins. In this setting, its grains do not take their typical crystal form. Sandstone, too, turns into a massive quartz rock called quartzite. Geological Significance of Quartz Among the common minerals, quartz is the toughest and most inert. It makes up the backbone of good soil, providing mechanical strength and holding open pore space between its grains. Its superior hardness and resistance to dissolution are what make sandstone and granite endure. Thus you could say that quartz holds up the mountains. Prospectors are always alert to veins of quartz because these are signs of hydrothermal activity and the possibility of ore deposits. To the geologist, the amount of silica in a rock is a basic and important bit of geochemical knowledge. Quartz is a ready sign of high silica, for example in rhyolite lava. Quartz is hard, stable, and low in density. When found in abundance, quartz always points to a continental rock because the tectonic processes that have built the Earths continents favor quartz.  As it moves through the tectonic cycle of erosion, deposition, subduction, and magmatism, quartz lingers in the uppermost crust and always comes out on top.

Green Revolution History and Overview

Green Revolution History and Overview The term Green Revolution refers to the renovation of agricultural practices beginning in Mexico in the 1940s. Because of its success in producing more agricultural products there, Green Revolution technologies spread worldwide in the 1950s and 1960s, significantly increasing the number of calories produced per acre of agriculture. History and Development of the Green Revolution The beginnings of the Green Revolution are often attributed to Norman Borlaug, an American scientist interested in agriculture. In the 1940s, he began conducting research in Mexico and developed new disease resistance high-yield varieties of wheat. By combining Borlaugs wheat varieties with new mechanized agricultural technologies, Mexico was able to produce more wheat than was needed by its own citizens, leading to them becoming an exporter of wheat by the 1960s. Prior to the use of these varieties, the country was importing almost half of its wheat supply. Due to the success of the Green Revolution in Mexico, its technologies spread worldwide in the 1950s and 1960s. The United States, for instance, imported about half of its wheat in the 1940s but after using Green Revolution technologies, it became self-sufficient in the 1950s and became an exporter by the 1960s. In order to continue using Green Revolution technologies to produce more food for a growing population worldwide, the Rockefeller Foundation and the Ford Foundation, as well as many government agencies around the world funded increased research. In 1963 with the help of this funding, Mexico formed an international research institution called The International Maize and Wheat Improvement Center. Countries all over the world, in turn, benefited from the Green Revolution work conducted by Borlaug and this research institution. India, for example, was on the brink of mass famine in the early 1960s because of its rapidly growing population. Borlaug and the Ford Foundation then implemented research there and they developed a new variety of rice, IR8, that produced more grain per plant when grown with irrigation and fertilizers. Today, India is one of the worlds leading rice producers and IR8 rice usage spread throughout Asia in the decades following the rices development in India. Plant Technologies of the Green Revolution The crops developed during the Green Revolution were high yield varieties - meaning they were domesticated plants bred specifically to respond to fertilizers and produce an increased amount of grain per acre planted. The terms often used with these plants that make them successful are harvest index, photosynthate allocation, and insensitivity to day length. The harvest index refers to the above-ground weight of the plant. During the Green Revolution, plants that had the largest seeds were selected to create the most production possible. After selectively breeding these plants, they evolved to all have the characteristic of larger seeds. These larger seeds then created more grain yield and a heavier above ground weight. This larger above ground weight then led to an increased photosynthate allocation. By maximizing the seed or food portion of the plant, it was able to use photosynthesis more efficiently because the energy produced during this process went directly to the food portion of the plant. Finally, by selectively breeding plants that were not sensitive to day length, researchers like Borlaug were able to double a crop’s production because the plants were not limited to certain areas of the globe based solely on the amount of light available to them. Impacts of the Green Revolution Since fertilizers are largely what made the Green Revolution possible, they forever changed agricultural practices because the high yield varieties developed during this time cannot grow successfully without the help of fertilizers. Irrigation also played a large role in the Green Revolution and this forever changed the areas where various crops can be grown. For instance, before the Green Revolution, agriculture was severely limited to areas with a significant amount of rainfall, but by using irrigation, water can be stored and sent to drier areas, putting more land into agricultural production - thus increasing nationwide crop yields. In addition, the development of high yield varieties meant that only a few species of say, rice started being grown. In India, for example, there were about 30,000 rice varieties prior to the Green Revolution, today there are around ten - all the most productive types. By having this increased crop homogeneity though the types were more prone to disease and pests because there were not enough varieties to fight them off. In order to protect these few varieties then, pesticide use grew as well. Finally, the use of Green Revolution technologies exponentially increased the amount of food production worldwide. Places like India and China that once feared famine have not experienced it since implementing the use of IR8 rice and other food varieties. Criticism of the Green Revolution Along with the benefits gained from the Green Revolution, there have been several criticisms. The first is that the increased amount of food production has led to overpopulation worldwide. The second major criticism is that places like Africa have not significantly benefited from the Green Revolution. The major problems surrounding the use of these technologies here though are a lack of infrastructure, governmental corruption, and insecurity in nations. Despite these criticisms though, the Green Revolution has forever changed the way agriculture is conducted worldwide, benefiting the people of many nations in need of increased food production.