Obsidian

Shale

Obsidian and Shale

Obsidian

Shale

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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

Shale is a fine-grained sedimentary rock which is formed by the compaction of silt and clay-size mineral particles

History

Origin

Ethiopia

Discoverer

Obsius

Johann Gottlob Lehmann

Etymology

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

From German Schalstein laminated limestone, and Schalgebirge layer of stone in stratified rock. From Old English scealu in its base sense of- thing that divides or separate,

Class

Igneous Rocks

Sedimentary Rocks

Sub-Class

Durable Rock, Medium Hardness Rock

Family

Group

Volcanic

Other Categories

Opaque Rock

Fine Grained Rock, Opaque Rock

Texture

Glassy

Clastic, Splintery

Color

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

Black, Brown, Buff, Green, Grey, Red, Yellow

Maintenance

Less

Durability

Durable

Water Resistant

✔ ✘

Scratch Resistant

✔ ✘

Stain Resistant

✔ ✘

Wind Resistant

✔ ✘

Acid Resistant

✔ ✘

Appearance

Shiny

Muddy

Uses

Architecture

Interior Uses

Decorative Aggregates, Interior Decoration

Decorative Aggregates, Homes, Interior Decoration

Exterior Uses

Garden Decoration

As Building Stone, As Facing Stone, Office Buildings

Other Architectural Uses

Curbing

Industry

Construction Industry

Arrowheads, Cutting Tool, Knives, Scrapers, Spear Points

Cement Manufacture, Construction Aggregate, for Road Aggregate, Making natural cement, Raw material for the manufacture of mortar

Medical Industry

Surgery

Antiquity Uses

Artifacts, Jewellery

Artifacts, Sculpture

Other Uses

Commercial Uses

Creating Artwork, Mirror, Used in aquariums

Creating Artwork, Pottery

Types

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

Red Shale, Black Shale, Green Shale, Grey Shale and Yellow Shale

Features

Blocks negativity, Helps to protect against depression

Easily splits into thin plates, Generally rough to touch, Very fine grained rock

Archaeological Significance

Monuments

Famous Monuments

Jantar Mantar in India

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.

Shale forms when very fine-grained clay particles are deposited in water which settle at the bottom of water bodies. They are later compacted hence forming shale.

Composition

Mineral Content

Albite, Biotite, Calcite, Chert, Chlorite, Dolomite, Hematite, Micas, Muscovite or Illite, Pyrite, Quartz, Silica, Sulfides

Compound Content

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

Ca, Fe, Mg, Silicon Dioxide, Sodium

Transformation

Metamorphism

✔ ✘

Types of Metamorphism

Burial Metamorphism, Cataclastic Metamorphism, Contact Metamorphism

Weathering

✔ ✘

Types of Weathering

Biological Weathering, Chemical Weathering, Mechanical Weathering

Erosion

✔ ✘

Types of Erosion

Chemical Erosion, Coastal Erosion, Glacier Erosion

Properties

Physical Properties

Hardness

5-5.53

1 7

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Grain Size

Very fine-grained

Fracture

Conchoidal

Streak

White

Porosity

Very Less Porous

Highly Porous

Luster

Vitreous

Dull

Compressive Strength

0.15 N/mm²95.00 N/mm²

0.15 450

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Cleavage

Slaty

Toughness

2.6

Specific Gravity

2.6-2.72.2-2.8

0 8.4

👆🏻

Transparency

Translucent

Opaque

Density

2.6 g/cm³2.4-2.8 g/cm³

0 1400

👆🏻

Thermal Properties

Specific Heat Capacity

0.92 kJ/Kg K0.39 kJ/Kg K

0.14 3.2

👆🏻

Resistance

Heat Resistant, Impact Resistant

Reserves

Deposits in Eastern Continents

Asia

Afghanistan, Indonesia, Japan, Russia

Bangladesh, China, India, Russia

Africa

Kenya

Ethiopia, Kenya, Morocco, South Africa, Tanzania

Europe

Greece, Hungary, Iceland, Italy, Turkey

Austria, France, Germany, Greece, Italy, Romania, Scotland, Spain, Switzerland

Others

Deposits in Western Continents

North America

Canada, Mexico, USA

USA

South America

Argentina, Chile, Ecuador, Peru

Bolivia, Chile, Colombia, Ecuador, Peru, Venezuela

Deposits in Oceania Continent

Australia

New Zealand

New South Wales, New Zealand, Queensland, Victoria, Western Australia

All about Obsidian and Shale Properties

Know all about Obsidian and Shale properties here. All properties of rocks are important as they define the type of rock and its application. Obsidian belongs to Igneous Rocks while Shale belongs to Sedimentary Rocks.Texture of Obsidian is Glassy whereas that of Shale is Clastic, Splintery. Obsidian appears Shiny and Shale appears Muddy. The luster of Obsidian is vitreous while that of Shale is dull. Obsidian is available in black, blue, brown, green, orange, red, tan, yellow colors whereas Shale is available in black, brown, buff, green, grey, red, yellow colors. The commercial uses of Obsidian are creating artwork, mirror, used in aquariums and that of Shale are creating artwork, pottery.