Obsidian

Greywacke

Obsidian and Greywacke

Obsidian

Greywacke

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Definition

Obsidian is a naturally occurring volcanic glass formed as an extrusive igneous rock. It is produced when felsic lava extruded from a volcano cools rapidly with minimum crystal growth

Greywacke is defined as a dark coarse-grained sandstone rock which contains more than 15 per cent clay

History

Origin

Ethiopia

Discoverer

Obsius

Unknown

Etymology

From Latin obsidianus, misprint of Obsianus (lapis) (stone) of Obsius

From German Grauwacke, from grau grey + wacke

Class

Igneous Rocks

Sedimentary Rocks

Sub-Class

Durable Rock, Medium Hardness Rock

Durable Rock, Hard Rock

Family

Group

Volcanic

Other Categories

Opaque Rock

Fine Grained Rock, Opaque Rock

Texture

Glassy

Clastic

Color

Black, Blue, Brown, Green, Orange, Red, Tan, Yellow

Beige, Black, Brown, Cream, Dark Brown, Green, Grey, Light Green, Light to Dark Grey, Pink, Red, White, Yellow

Maintenance

Less

Durability

Durable

Water Resistant

✔ ✘

Scratch Resistant

✔ ✘

Stain Resistant

✔ ✘

Wind Resistant

✔ ✘

Acid Resistant

✔ ✘

Appearance

Shiny

Dull

Uses

Architecture

Interior Uses

Decorative Aggregates, Interior Decoration

Decorative Aggregates, Floor Tiles, Flooring, Homes, Interior Decoration

Exterior Uses

Garden Decoration

As Building Stone, As Facing Stone, Garden Decoration, Office Buildings, Paving Stone

Other Architectural Uses

Curbing, Whetstones

Industry

Construction Industry

Arrowheads, Cutting Tool, Knives, Scrapers, Spear Points

Building houses or walls, Cement Manufacture, Construction Aggregate, for Road Aggregate, Raw material for the manufacture of mortar

Medical Industry

Surgery

Antiquity Uses

Artifacts, Jewellery

Artifacts, Sculpture, Small Figurines

Other Uses

Commercial Uses

Creating Artwork, Mirror, Used in aquariums

As armour rock for sea walls, Petroleum reservoirs, Sea Defence, Tombstones

Types

Fireworks Obsidian, Mahogany, Sheen Obsidian, Snowflake obsidian and Velvet Peacock Obsidian

Greywacke

Features

Blocks negativity, Helps to protect against depression

Available in Lots of Colors and Patterns, Generally rough to touch, Non-vesicular, Veined

Archaeological Significance

Monuments

Famous Monuments

Sculpture

Famous Sculptures

Pictographs

Petroglyphs

Figurines

Fossils

Absent

Present

Formation

When the lava is released from volcano, it undergoes a very rapid cooling which freezes the mechanisms of crystallization. The result is a volcanic glass with a uniform smooth texture.

Graywacke rock is a type of sedimentary rock, which is also known as immature sandstone, which is indurated, dark grey and consisting of poorly sorted angular to sub-angular, sand-sized grains.

Composition

Mineral Content

Augite, Biotite, Calcite, Chlorite, Clay, Clay Minerals, Feldspar, Micas, Muscovite or Illite, Plagioclase, Pyroxene, Quartz

Compound Content

Aluminium Oxide, CaO, Iron(III) Oxide, FeO, Potassium Oxide, MgO, MnO, Sodium Oxide, Phosphorus Pentoxide, Silicon Dioxide, Titanium Dioxide

Aluminium Oxide, NaCl, CaO, Chromium(III) Oxide, Iron(III) Oxide, FeO, Potassium Oxide, Magnesium Carbonate, MgO, MnO, Sodium Oxide, Phosphorus Pentoxide, Silicon Dioxide, Titanium Dioxide

Transformation

Metamorphism

✔ ✘

Types of Metamorphism

Burial Metamorphism, Cataclastic Metamorphism, Contact Metamorphism

Weathering

✔ ✘

Types of Weathering

Biological Weathering, Chemical Weathering, Mechanical Weathering

Biological Weathering, Chemical Weathering

Erosion

✔ ✘

Types of Erosion

Chemical Erosion, Coastal Erosion, Glacier Erosion

Coastal Erosion, Sea Erosion, Wind Erosion

Properties

Physical Properties

Hardness

5-5.56-7

1 7

👆🏻

Grain Size

Angular and Fine

Fracture

Conchoidal

Streak

White

Porosity

Very Less Porous

Highly Porous

Luster

Vitreous

Dull

Compressive Strength

0.15 N/mm²120.00 N/mm²

0.15 450

👆🏻

Cleavage

Perfect

Toughness

2.6

Specific Gravity

2.6-2.72.2-2.8

0 8.4

👆🏻

Transparency

Translucent

Opaque

Density

2.6 g/cm³2.6-2.61 g/cm³

0 1400

👆🏻

Thermal Properties

Specific Heat Capacity

0.92 kJ/Kg K0.71 kJ/Kg K

0.14 3.2

👆🏻

Resistance

Heat Resistant, Impact Resistant

Heat Resistant, Impact Resistant, Pressure Resistant

Reserves

Deposits in Eastern Continents

Asia

Afghanistan, Indonesia, Japan, Russia

China, India, Kazakhstan, Mongolia, Russia, Uzbekistan

Africa

Kenya

Namibia, Nigeria, South Africa

Europe

Greece, Hungary, Iceland, Italy, Turkey

Austria, Denmark, Germany, Great Britain, Netherlands, Norway, Poland, Sweden, Switzerland, United Kingdom

Others

Greenland

Deposits in Western Continents

North America

Canada, Mexico, USA

Canada, USA

South America

Argentina, Chile, Ecuador, Peru

Brazil

Deposits in Oceania Continent

Australia

New Zealand

New South Wales, New Zealand

All about Obsidian and Greywacke Properties

Know all about Obsidian and Greywacke properties here. All properties of rocks are important as they define the type of rock and its application. Obsidian belongs to Igneous Rocks while Greywacke belongs to Sedimentary Rocks.Texture of Obsidian is Glassy whereas that of Greywacke is Clastic. Obsidian appears Shiny and Greywacke appears Dull. The luster of Obsidian is vitreous while that of Greywacke is dull. Obsidian is available in black, blue, brown, green, orange, red, tan, yellow colors whereas Greywacke is available in beige, black, brown, cream, dark brown, green, grey, light green, light to dark grey, pink, red, white, yellow colors. The commercial uses of Obsidian are creating artwork, mirror, used in aquariums and that of Greywacke are as armour rock for sea walls, petroleum reservoirs, sea defence, tombstones.