Obsidian

Gneiss

Obsidian and Gneiss

Obsidian

Gneiss

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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

Gneiss is a common and widely distributed type of rock formed by high-grade regional metamorphic processes from pre-existing formations that were originally either igneous or sedimentary rocks

History

Origin

Ethiopia

Discoverer

Obsius

Unknown

Etymology

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

From the Middle High German verb gneist (to spark; so called because the rock glitters)

Class

Igneous Rocks

Metamorphic Rocks

Sub-Class

Durable Rock, Medium Hardness Rock

Durable Rock, Hard Rock

Family

Group

Volcanic

Other Categories

Opaque Rock

Coarse Grained Rock, Medium Grained Rock, Opaque Rock

Texture

Glassy

Banded, Foliated, Platy

Color

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

Black, Brown, Pink, Red, White

Maintenance

Less

Durability

Durable

Water Resistant

✔ ✘

Scratch Resistant

✔ ✘

Stain Resistant

✔ ✘

Wind Resistant

✔ ✘

Acid Resistant

✔ ✘

Appearance

Shiny

Foliated

Uses

Architecture

Interior Uses

Decorative Aggregates, Interior Decoration

Countertops, Decorative Aggregates, Flooring, Interior Decoration

Exterior Uses

Garden Decoration

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

Other Architectural Uses

Curbing

Industry

Construction Industry

Arrowheads, Cutting Tool, Knives, Scrapers, Spear Points

As Dimension Stone

Medical Industry

Surgery

Antiquity Uses

Artifacts, Jewellery

Artifacts

Other Uses

Commercial Uses

Creating Artwork, Mirror, Used in aquariums

Cemetery Markers, Jewelry, Tombstones, Used in aquariums

Types

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

Augen Gneiss, Henderson Gneiss, Lewisian Gneiss, Archean and Proterozoic Gneiss.

Features

Blocks negativity, Helps to protect against depression

Generally rough to touch, Is one of the oldest rock

Archaeological Significance

Monuments

Famous Monuments

Konark Sun Temple in India, Washington Monument, US

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.

Gneiss is a high grade metamorphic rock i.e. it has been subjected to higher temperatures and pressures than schist. It is formed by the metamorphosis of Gneiss forms from volcanic rock, shale or granitie.

Composition

Mineral Content

Biotite, Chlorite, Feldspar, Garnet, Graphite, Hornblade, Micas, Muscovite or Illite, Quartz, Quartzite, Silica, Zircon

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, Iron(III) Oxide, FeO, Potassium Oxide, Magnesium Carbonate, MgO, MnO, Phosphorus Pentoxide, Silicon Dioxide, Titanium Dioxide

Transformation

Metamorphism

✔ ✘

Types of Metamorphism

Burial Metamorphism, Cataclastic Metamorphism, Contact Metamorphism

Impact Metamorphism

Weathering

✔ ✘

Types of Weathering

Biological Weathering, Chemical Weathering, Mechanical Weathering

Biological Weathering, Mechanical Weathering

Erosion

✔ ✘

Types of Erosion

Chemical Erosion, Coastal Erosion, Glacier Erosion

Chemical Erosion, Coastal Erosion, Sea Erosion

Properties

Physical Properties

Hardness

5-5.57

1 7

👆🏻

Grain Size

Medium to Coarse Grained

Fracture

Conchoidal

Irregular

Streak

White

Porosity

Very Less Porous

Luster

Vitreous

Dull

Compressive Strength

0.15 N/mm²125.00 N/mm²

0.15 450

👆🏻

Cleavage

Toughness

1.2

Specific Gravity

2.6-2.72.5-2.7

0 8.4

👆🏻

Transparency

Translucent

Translucent to Opaque

Density

2.6 g/cm³2.6-2.9 g/cm³

0 1400

👆🏻

Thermal Properties

Specific Heat Capacity

0.92 kJ/Kg K0.70 kJ/Kg K

0.14 3.2

👆🏻

Resistance

Heat Resistant, Impact Resistant

Heat Resistant, Pressure Resistant, Scratch Resistant, Wear Resistant

Reserves

Deposits in Eastern Continents

Asia

Afghanistan, Indonesia, Japan, Russia

China, India, Iran, Iraq, Kazakhstan, Kyrgyzstan, Mongolia, Russia

Africa

Kenya

Cameroon, Ethiopia, Ghana, Kenya, Madagascar, Morocco, Mozambique, Namibia, Nigeria, Tanzania, Togo

Europe

Greece, Hungary, Iceland, Italy, Turkey

Albania, Austria, Bosnia and Herzegovina, Finland, France, Georgia, Germany, Hungary, Italy, Kosovo, Monaco, Norway, Poland, Romania, Serbia, Slovakia, Slovenia, Switzerland, Ukraine, United Kingdom

Others

Deposits in Western Continents

North America

Canada, Mexico, USA

Canada, Costa Rica, Cuba, Mexico, Panama, USA

South America

Argentina, Chile, Ecuador, Peru

Argentina, Bolivia, Brazil, Chile, Colombia, Ecuador, Peru, Venezuela

Deposits in Oceania Continent

Australia

New Zealand

New South Wales, New Zealand, Queensland, Victoria

All about Obsidian and Gneiss Properties

Know all about Obsidian and Gneiss properties here. All properties of rocks are important as they define the type of rock and its application. Obsidian belongs to Igneous Rocks while Gneiss belongs to Metamorphic Rocks.Texture of Obsidian is Glassy whereas that of Gneiss is Banded, Foliated, Platy. Obsidian appears Shiny and Gneiss appears Foliated. The luster of Obsidian is vitreous while that of Gneiss is dull. Obsidian is available in black, blue, brown, green, orange, red, tan, yellow colors whereas Gneiss is available in black, brown, pink, red, white colors. The commercial uses of Obsidian are creating artwork, mirror, used in aquariums and that of Gneiss are cemetery markers, jewelry, tombstones, used in aquariums.