Obsidian

Argillite

Obsidian and Argillite

Obsidian

Argillite

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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

Argillites are highly compact sedimentary or slightly metamorphosed rocks that consist largely or wholly of particles of clay or silt but lack the fissility of shale or the cleavage characteristic of slate

History

Origin

Ethiopia

Discoverer

Obsius

Unknown

Etymology

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

From Latin Argilla (clay) and -ite in English which became agrilla+ -ite = Argillite

Class

Igneous Rocks

Sedimentary Rocks

Sub-Class

Durable Rock, Medium Hardness Rock

Durable Rock, Soft Rock

Family

Group

Volcanic

Other Categories

Opaque Rock

Fine Grained Rock, Opaque Rock

Texture

Glassy

Clastic, Polished

Color

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

Dark Grey to Black, Pink, Red, White

Maintenance

Less

Durability

Durable

Water Resistant

✔ ✘

Scratch Resistant

✔ ✘

Stain Resistant

✔ ✘

Wind Resistant

✔ ✘

Acid Resistant

✔ ✘

Appearance

Shiny

Rough and Dull

Uses

Architecture

Interior Uses

Decorative Aggregates, Interior Decoration

Decorative Aggregates, Homes, Interior Decoration

Exterior Uses

Garden Decoration

As Building Stone, Garden Decoration, Office Buildings

Other Architectural Uses

Curbing, Whetstones

Industry

Construction Industry

Arrowheads, Cutting Tool, Knives, Scrapers, Spear Points

Used for flooring, stair treads, borders and window sills.

Medical Industry

Surgery

Antiquity Uses

Artifacts, Jewellery

Artifacts, Monuments, Sculpture

Other Uses

Commercial Uses

Creating Artwork, Mirror, Used in aquariums

Fire resistant, Used to manufracture paperweights and bookends

Types

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

Metamorphic rock

Features

Blocks negativity, Helps to protect against depression

Is one of the oldest rock

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.

An argillite is a fine-grained sedimentary rock mainly composed of clay particles which forms from lithified muds which contain variable amounts of silt-sized particles.

Composition

Mineral Content

Biotite, Chlorite, Feldspar, Micas, Muscovite or Illite, Plagioclase, Pyrite, Quartz

Compound Content

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

Iron(III) Oxide, Potassium Oxide, MgO, Silicon Dioxide

Transformation

Metamorphism

✔ ✘

Types of Metamorphism

Burial Metamorphism, Cataclastic Metamorphism, Contact Metamorphism

Weathering

✔ ✘

Types of Weathering

Biological Weathering, Chemical Weathering, Mechanical Weathering

Biological Weathering

Erosion

✔ ✘

Types of Erosion

Chemical Erosion, Coastal Erosion, Glacier Erosion

Chemical Erosion

Properties

Physical Properties

Hardness

5-5.52-3

1 7

👆🏻

Grain Size

Fine Grained

Fracture

Conchoidal

Conchoidal to Uneven

Streak

White

White to Grey

Porosity

Very Less Porous

Highly Porous

Luster

Vitreous

Waxy and Dull

Compressive Strength

0.15 N/mm²-

0.15 450

👆🏻

Cleavage

Slaty

Toughness

2.6

Specific Gravity

2.6-2.72.56-2.68

0 8.4

👆🏻

Transparency

Translucent

Opaque

Density

2.6 g/cm³2.54-2.66 g/cm³

0 1400

👆🏻

Thermal Properties

Specific Heat Capacity

0.92 kJ/Kg K0.87 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 Argillite Properties

Know all about Obsidian and Argillite properties here. All properties of rocks are important as they define the type of rock and its application. Obsidian belongs to Igneous Rocks while Argillite belongs to Sedimentary Rocks.Texture of Obsidian is Glassy whereas that of Argillite is Clastic, Polished. Obsidian appears Shiny and Argillite appears Rough and Dull. The luster of Obsidian is vitreous while that of Argillite is waxy and dull. Obsidian is available in black, blue, brown, green, orange, red, tan, yellow colors whereas Argillite is available in dark grey to black, pink, red, white colors. The commercial uses of Obsidian are creating artwork, mirror, used in aquariums and that of Argillite are fire resistant, used to manufracture paperweights and bookends.