Obsidian

Tephrite

Obsidian and Tephrite

Obsidian

Tephrite

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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

Tephrite is an aphanitic to porphyritic textured, volcanic igneous rock

History

Origin

Ethiopia

Germany

Discoverer

Obsius

Van Tooren

Etymology

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

From Greek tephra, ashes from Indo-European base, to burn

Class

Igneous Rocks

Sub-Class

Durable Rock, Medium Hardness Rock

Durable Rock, Hard Rock

Family

Group

Volcanic

Other Categories

Opaque Rock

Coarse Grained Rock, Fine Grained Rock, Medium Grained Rock, Opaque Rock

Texture

Glassy

Aphanitic to Porphyritic

Color

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

Black, Brown, Green, Grey, White

Maintenance

Less

Durability

Durable

Water Resistant

✔ ✘

Scratch Resistant

✔ ✘

Stain Resistant

✔ ✘

Wind Resistant

✔ ✘

Acid Resistant

✔ ✘

Appearance

Shiny

Vesicular

Uses

Architecture

Interior Uses

Decorative Aggregates, Interior Decoration

Decorative Aggregates, Flooring, Homes, Interior Decoration

Exterior Uses

Garden Decoration

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

Other Architectural Uses

Curbing

Industry

Construction Industry

Arrowheads, Cutting Tool, Knives, Scrapers, Spear Points

Landscaping

Medical Industry

Surgery

Antiquity Uses

Artifacts, Jewellery

Artifacts, Sculpture

Other Uses

Commercial Uses

Creating Artwork, Mirror, Used in aquariums

Production of Lime, Soil Conditioner

Types

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

Igneous rock

Features

Blocks negativity, Helps to protect against depression

Host Rock for Lead

Archaeological Significance

Monuments

Famous Monuments

Sculpture

Famous Sculptures

Pictographs

Petroglyphs

Figurines

Fossils

Absent

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.

Tephrite is a fine-grained, hard rock which is a type of metasomatite, essentially altered basalt. It forms with or without crystallization, either below the surface as intrusive rocks or on the surface as extrusive rocks.

Composition

Mineral Content

Alkali feldspar, Nepheline, Plagioclase, Pyroxene

Compound Content

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

CaO, Carbon Dioxide, MgO, Silicon Dioxide

Transformation

Metamorphism

✔ ✘

Types of Metamorphism

Burial Metamorphism, Cataclastic Metamorphism, Contact Metamorphism

Cataclastic Metamorphism, Contact Metamorphism, Impact Metamorphism, Regional Metamorphism

Weathering

✔ ✘

Types of Weathering

Biological Weathering, Chemical Weathering, Mechanical Weathering

Erosion

✔ ✘

Types of Erosion

Chemical Erosion, Coastal Erosion, Glacier Erosion

Chemical Erosion, Coastal Erosion, Glacier Erosion, Sea Erosion, Water Erosion

Properties

Physical Properties

Hardness

5-5.56.5

1 7

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Grain Size

Medium to Fine Coarse Grained

Fracture

Conchoidal

Uneven

Streak

White

Bluish Black

Porosity

Very Less Porous

Luster

Vitreous

Subvitreous to Dull

Compressive Strength

0.15 N/mm²90.00 N/mm²

0.15 450

👆🏻

Cleavage

Crenulation and Pervasive

Toughness

2.4

Specific Gravity

2.6-2.72.86

0 8.4

👆🏻

Transparency

Translucent

Opaque

Density

2.6 g/cm³2.8-2.9 g/cm³

0 1400

👆🏻

Thermal Properties

Specific Heat Capacity

0.92 kJ/Kg K0.92 kJ/Kg K

0.14 3.2

👆🏻

Resistance

Heat Resistant, Impact Resistant

Reserves

Deposits in Eastern Continents

Asia

Afghanistan, Indonesia, Japan, Russia

Africa

Kenya

Namibia, Uganda

Europe

Greece, Hungary, Iceland, Italy, Turkey

Germany, Hungary, Italy, Portugal, Spain

Others

Deposits in Western Continents

North America

Canada, Mexico, USA

USA

South America

Argentina, Chile, Ecuador, Peru

Deposits in Oceania Continent

Australia

New Zealand

New Zealand, Western Australia

All about Obsidian and Tephrite Properties

Know all about Obsidian and Tephrite properties here. All properties of rocks are important as they define the type of rock and its application. Obsidian and Tephrite belong to Igneous Rocks.Texture of Obsidian is Glassy whereas that of Tephrite is Aphanitic to Porphyritic. Obsidian appears Shiny and Tephrite appears Vesicular. The luster of Obsidian is vitreous while that of Tephrite is subvitreous to dull. Obsidian is available in black, blue, brown, green, orange, red, tan, yellow colors whereas Tephrite is available in black, brown, green, grey, white colors. The commercial uses of Obsidian are creating artwork, mirror, used in aquariums and that of Tephrite are production of lime, soil conditioner.