These tend to be of rare and unusual rock types. Many rare minerals are found associated with them or in the altered zones of the immediately surrounding rocks. The post-Cretaceous age deposits of the Western Gulf Coastal Plain and the Mississippi River Alluvial Plain of southern and eastern Arkansas are underlain by sand, silt, clay, and gravel.
Most of these deposits are not lithified, but there is some limonite iron oxides cementation of some layers and nodules in places. The thickest exposures of loess are toward the southern end of the ridge. In a few places on the northern end of the ridge on the west side, sandstone with quartz cement called quartzite also occurs. Thirteen minerals were first discovered in Arkansas.
Most of these minerals were named for the people who found them or were important in their discovery. All are somewhat rare. For additional information: Arkansas Geological Survey. Haley, B. Geologic Map of Arkansas.
Little Rock: Arkansas Geological Commission, Howard, J. Mineral Species of Arkansas, A Digest. Arkansas Geological Commission Bulletin Michael, George W. Colton, and William L. McFarland, John David.
Stratigraphic Summary of Arkansas. Arkansas Geological Commission Information Circular McFarland, John David, and J. Michael Howard. Minerals of Arkansas: An Electronic Database. Stroud, R. Mineral Resources and Industries of Arkansas. Bureau of Mines Bulletin Washington DC: U. Department of the Interior, Bureau of Mines, Honor or memorial gifts are an everlasting way to pay tribute to someone who has touched your life. When a tribute gift is given the honoree will receive a letter acknowledging your generosity and a bookplate will be placed in a book.
For more information, contact or calsfoundation cals. Read our Privacy Policy. Quartz clear, glassy mineral crystallizes later and fills spaces. Characteristics: Coarse-grained — The grains, or crystals, are big enough to tell what mineral each one is. The crystals are usually larger than 1 millimeter larger than the point of a pen or pencil.
The edges of the crystals interlock. The crystals are shiny, flat surfaces which fit together like jigsaw puzzle pieces, with straight edges on some crystals. The minerals are very hard and will scratch glass. If the rock has been weathered by the elements, it may be crumbly. The texture is generally uniform the same in all directions. They cool quickly with no time for large crystals to grow. They are, thus, very fine grained. Mineral composition can only be identified with a microscope unless phenocrysts are present see below.
Field identification of hand specimens is based on light or dark color, unless phenocrysts are present. Characteristics: Fine-grained — The grains are too fine to identify the minerals without a microscope.
Very hard! Specimens will scratch glass, although it will be crumbly if it has been out in the weather for a long time. Some volcanic rocks have vesicles, which are holes caused by gas bubbles when the lava was molten. Porphyritic phaneritic: Smaller crystals surround larger crystals phenocrysts. Porphyritic aphanitic: Massive, structureless ground mass surrounds crystals phenocrysts.
Vitrophyre is a glassy rock containing crystals phenocrysts. Obsidian is a black glass with conchoidal circular fracture. Perfect cleavage in 1 direction layers Orthoclase K-feldspar : Porcelain luster; commonly colored pink, white, or gray. Silica Si and Oxygen O are the only elements within pure quartz.
If a cooling magma has silica leftover after feldspars form, quartz is likely They sparkle because light is reflected on their flat surfaces, which It is found it all of the three rock types, but is most common in intrusive igneous Olivine Olivine looks like little green crystals.
It is typically found in some igneous and metamorphic rocks. Often the crystals are so small that you need to use your hand lens or magnifying glass to see them Please log in Username: Password: Forgot password? NESTA welcomes new Institutional Affiliates in support of our ongoing programs, as well as collaborations on new projects. All Rights Reserved. See our copyright and licenses page for information about how you can use our materials.
Site policies and disclaimer. Biotite Shape: Monoclinic. Precious metals are rare, naturally occurring metallic chemical elements of high economic value. Chemically, they tend to be less reactive than most elements.
They are usually ductile and have a high lustre. In history precious metals were important as currency but are now regarded mainly as investment and industrial commodities. The main examples of precious metals are Gold, Silver and Platinum. Some examples of precious metals found in Ireland are; 1. Gold Gold is a valuable, yellow metal.
Gold is usually found in metamorphic rock. It is found in underground veins of rock where the inside of the Earth heats the water that flows through the rock. Gold has been important all throughout history, it was used in important events by the ancient Egyptians and was important in Bronze Age Ireland. Due to both it beauty and its durability it is regularly used in jewellery and as a form of currency.
Trace amounts of gold are found almost everywhere, but large deposits are found in only a few locations. Platinum Platinum is a valuable grey-white metal. It is dense, malleable, ductile and highly unreactive metal. It has a wide variety of uses including use in catalytic converters, electrical contacts, dentistry equipment, and jewellery.
Platinum has recently been identified in stream samples taken by the Geological Survey between and The samples were reanalysed in using modern laboratory techniques by the Tellus team. The samples showed an extensive zone of high platinum concentration in Co. Gemstones are minerals or rocks that can be cut, shaped, and polished into beautiful stones that can be used in jewellery and for collecting.
A stone is worth more money if it is perfect. Most gemstones are minerals and have the same characteristics as minerals do however, some organic materials such as Amber and Coral are also considered gems. Gems endure through time as they are resistant to chemical alteration, are sufficiently hard to retain a good polish and are not easily chipped or broken.
Types of gem include emerald, ruby and sapphire. Page Content. Some of the most common ones and their uses are: Asbestos [image left] has an unsavory reputation for causing cancer in people who work around it. Lead and Zinc Lead and Zinc, and sometimes silver, are usually found occurring together. Precious metals Precious metals are rare, naturally occurring metallic chemical elements of high economic value.
Gems Gemstones are minerals or rocks that can be cut, shaped, and polished into beautiful stones that can be used in jewellery and for collecting. Its name derives from the Greek "amethystos", which means "not drunken" - it was once thought to ward off drunkenness.
Discoveries of huge Amethyst deposits since the 's have made Amethyst inexpensive and easier to find. Amethyst colors range from light to dark purple, and the transparent deep purple colors are the most highly regarded. In fact, they are so hard that the only things that will cut them are other diamonds. Diamond, like charcoal and graphite is a form of carbon. In fact, it is unique among gems as it is comprised of just one chemical - carbon. Diamond varies in colour from colourless to yellows, browns, greens, blues, pinks and a very rare red.
Most are tinged with yellow or brown. The most prized are the rare red or rare colourless. Diamonds were known in India years ago.
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