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We know three main classes of rocks, sedimentary, igneous, and metamorphic. In Limestone article, we learned how sedimentation occurs, and the formation of sedimentary rocks takes place. Today, we are going to know Obsidian rock, which falls in the main class igneous rocks.
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Introduction • We know three main classes of rocks, sedimentary, igneous, and metamorphic. In Limestone article, we learned how sedimentation occurs, and the formation of sedimentary rocks takes place. Today, we are going to know Obsidian rock, which falls in the main class igneous rocks. • We know igneous rocks have two basic types.
1. Intrusive Igneous Rocks • When molten lava/magma is cooling slowly below the surface of the earth and forms large crystals in the rocks they known as intrusive igneous rocks.
2 – Extrusive Igneous Rocks • When molten magma is cooling rapidly onto the surface of the earth and forms small crystals in the rocks they known as extrusive igneous rocks.
What Is Obsidian Rock? • Obsidian is a class of igneous rocks, which forms when felsic lava extruded from a volcano onto the surface of the earth. • The cooling of lava takes place so rapidly that no chance remains for proper crystallization (Atomic Arrangements) and finds as an amorphous glass material. It has a smooth and uniform texture, which breaks with a conchoidal fracture.
Formation of Obsidian Rocks in Nature • The obsidian formation can happen in a variety of cooling environment such as • Along the edges of a flow of magma or lava • Along the edges of a dome of the volcano • Along the edges of a sill or dike, which takes place under the surface and it is the only intrusive type • The point where magma comes into the contact of water on the surface • The point where magma cools due to airborne cooling effects
Streaks & Colors of Obsidian The streak of obsidian is white, but various colors occur in nature. Frequently found colors of Obsidian rocks are: • The highest occurrence of obsidians is in Black, but it also available in Brown, Green, or Tan. Rarely found colors of Obsidian rocks are: • A very rare occurrence of obsidians is in Blue, Orange, Red, and Yellow. • The occurrence of color is due to the presence of different trace elements in obsidian rocks.
The hardness of Obsidian (How Hard Is Obsidian Rocks) • In physics and geology, the hardness of the physical objects or rocks is measured in Moh’s scale, which rates the objects in question on the scale from 1 to 10. • Rocks with Moh’s hardness scale from 1 to 3 are considering soft rocks. • From 3 to 6 scale – medium hardness • From 6 to 10 hardness scale – the hardest rocks. • It also means obsidian is easy to scratch.
Compressive Strength of Obsidian • When a compressive pressure (In Newton unit) applied on the rocks a permanent deformation of rocks takes place at a point of pressure. It is termed as the compressive strength of rocks and obsidians fractured or permanently deformed at 0.15 N per square millimeter. It means obsidian is easy to break and chipped by some impacts. It also renders obsidian as the unfit stone for rings and bracelets like jewelry production.
Obsidian Fracture • Obsidians breaks into the conchoidal fracture. Obsidian has no natural or defined planes of separation when a pressure exceeding from its physical strength exerts on it. Therefore, smoothly curved fracture takes place on the surface of obsidian glass rock. • The images at the side are depicting the phenomena beautifully and precisely.
Specific Gravity & Density of Obsidian The density of rock used to expresses as specific gravity, and it is measured in relevance to the density of water in gram per cubic centimeter of the mass. The density of obsidian is 2.55 g/cubic cm. It means it is heavier than water and dense medium as a mass. Luster & Transparency of Obsidian In Obsidian, only 1% of water exists. It means it is vitreous and due to the high presence of silica and other glass-forming minerals, it is translucent in transparency.
Mahogany Obsidian Snowflake Obsidian Rainbow Obsidian Gold Sheen Obsidian Silver Sheen Obsidian
Purple Sheen Obsidian Double Flow Obsidian Black Obsidian Pumpkin Obsidian Green Obsidian
The occurrence of Obsidian Rocks in Different Geographic Regions of the Earth
Obsidians as Weapons & Tools • The human civilization has used obsidian rocks to make knives, spear points, arrowheads, scrapers, and various weapons. • Knives and blades were fine for kitchen applications. Scrappers were used in land digging, agriculture, and gardening applications. Arrowheads and spear points were provided the sharpest tools for warriors in the creation of various weapons.
Obsidians in Construction Industry • Obsidian rocks use in interior and exterior decoration. Decorative aggregates, gravels, and pebbles from obsidian rocks are a favorite material for creating architectural beauty and artwork on walls, ceilings, and floors of the buildings. Artworks in gardens, patios, swimming pools, fire features, and water features look amazing when obsidian rocks applied along with other Gemstones.
Obsidians in Medical Surgery • If you look at the sharpest edge of the steel blade in the microscope, you will notice almost saw-like teeth on edge. Whereas, the obsidian blade has no bite because it has evenly sooth edge at the microscopic level. Therefore, wounds cut by obsidian blades are healing significantly faster than wounds by steel blades. • obsidian can produce the sharpest materials that only Nanotechnologies can produce.
Obsidians in Antiquity and Jewelry Industry • However, medium strength of obsidian with 5.5 hardness creates durability concerns and the jewelry industry avoid its use as they apply diamonds and other gemstones.
Obsidian Rocks for Sales Spiderweb Apache Tears Cat Eye
Obsidian Rocks for Sales Peanut Flame/Fire Midnight Lace
Conclusion • In the series of identifying various rocks and natural stones at World of Stones, USA, we have explored different aspects of obsidian rocks such as meaning, uses, facts, properties, and colors of obsidians. • World of Stones, USA is an excellent place to buy a variety of natural rocks mainly used for exterior applications in building construction industry. If you are interested to know about rocks and stones, keep the reading of blogs at World of Stones.
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Source • https://worldofstonesusa.com/blog/obsidian-rock/
