Gneiss

Obsidian

Gneiss and Obsidian

Gneiss

Obsidian

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Definition

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

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

History

Origin

Ethiopia

Discoverer

Unknown

Obsius

Etymology

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

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

Class

Metamorphic Rocks

Igneous Rocks

Sub-Class

Durable Rock, Hard Rock

Durable Rock, Medium Hardness Rock

Family

Group

Volcanic

Other Categories

Coarse Grained Rock, Medium Grained Rock, Opaque Rock

Opaque Rock

Texture

Banded, Foliated, Platy

Glassy

Color

Black, Brown, Pink, Red, White

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

Maintenance

Less

Durability

Durable

Water Resistant

✔ ✘

Scratch Resistant

✔ ✘

Stain Resistant

✔ ✘

Wind Resistant

✔ ✘

Acid Resistant

✔ ✘

Appearance

Foliated

Shiny

Uses

Architecture

Interior Uses

Countertops, Decorative Aggregates, Flooring, Interior Decoration

Decorative Aggregates, Interior Decoration

Exterior Uses

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

Garden Decoration

Other Architectural Uses

Curbing

Industry

Construction Industry

As Dimension Stone

Arrowheads, Cutting Tool, Knives, Scrapers, Spear Points

Medical Industry

Surgery

Antiquity Uses

Artifacts

Artifacts, Jewellery

Other Uses

Commercial Uses

Cemetery Markers, Jewelry, Tombstones, Used in aquariums

Creating Artwork, Mirror, Used in aquariums

Types

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

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

Features

Generally rough to touch, Is one of the oldest rock

Blocks negativity, Helps to protect against depression

Archaeological Significance

Monuments

Famous Monuments

Konark Sun Temple in India, Washington Monument, US

Sculpture

Famous Sculptures

Pictographs

Petroglyphs

Figurines

Fossils

Absent

Formation

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.

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.

Composition

Mineral Content

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

Compound Content

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

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

Transformation

Metamorphism

✔ ✘

Types of Metamorphism

Impact Metamorphism

Burial Metamorphism, Cataclastic Metamorphism, Contact Metamorphism

Weathering

✔ ✘

Types of Weathering

Biological Weathering, Mechanical Weathering

Biological Weathering, Chemical Weathering, Mechanical Weathering

Erosion

✔ ✘

Types of Erosion

Chemical Erosion, Coastal Erosion, Sea Erosion

Chemical Erosion, Coastal Erosion, Glacier Erosion

Properties

Physical Properties

Hardness

75-5.5

1 7

👆🏻

Grain Size

Medium to Coarse Grained

Fracture

Irregular

Conchoidal

Streak

White

Porosity

Very Less Porous

Luster

Dull

Vitreous

Compressive Strength

125.00 N/mm²0.15 N/mm²

0.15 450

👆🏻

Cleavage

Toughness

1.2

Specific Gravity

2.5-2.72.6-2.7

0 8.4

👆🏻

Transparency

Translucent to Opaque

Translucent

Density

2.6-2.9 g/cm³2.6 g/cm³

0 1400

👆🏻

Thermal Properties

Specific Heat Capacity

0.70 kJ/Kg K0.92 kJ/Kg K

0.14 3.2

👆🏻

Resistance

Heat Resistant, Pressure Resistant, Scratch Resistant, Wear Resistant

Heat Resistant, Impact Resistant

Reserves

Deposits in Eastern Continents

Asia

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

Afghanistan, Indonesia, Japan, Russia

Africa

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

Kenya

Europe

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

Greece, Hungary, Iceland, Italy, Turkey

Others

Deposits in Western Continents

North America

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

Canada, Mexico, USA

South America

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

Argentina, Chile, Ecuador, Peru

Deposits in Oceania Continent

Australia

New South Wales, New Zealand, Queensland, Victoria

New Zealand

All about Gneiss and Obsidian Properties

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