Schist

Pseudotachylite

Schist and Pseudotachylite

Schist

Pseudotachylite

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Definition

Schist is a medium grade metamorphic rock with medium to large, flat, sheet like grains in a preferred orientation

Very fine grained fault rock which is composed of glassy matrix that often contains inclusions of wall-rock fragments.

History

Origin

USA

Discoverer

Unknown

Etymology

From French schiste, Greek skhistos i.e. split

From pseudo- +‎ tachylite, a glassy rock generated by frictional heat within faults.

Class

Metamorphic Rocks

Sub-Class

Durable Rock, Medium Hardness Rock

Durable Rock, Hard Rock

Family

Group

Other Categories

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

Fine Grained Rock, Opaque Rock

Texture

Foliated, Platy

Quench

Color

Black, Blue, Brown, Dark Brown, Green, Grey, Silver

Black, Brown, Green, Grey, Pink, White

Maintenance

Less

Durability

Durable

Water Resistant

✔ ✘

Scratch Resistant

✔ ✘

Stain Resistant

✔ ✘

Wind Resistant

✔ ✘

Acid Resistant

✔ ✘

Appearance

Layered and Shiny

Dull and Soft

Uses

Architecture

Interior Uses

Decorative Aggregates, Floor Tiles, Interior Decoration

Decorative Aggregates, Entryways, Interior Decoration

Exterior Uses

Garden Decoration, Paving Stone

As Building Stone, As Facing Stone, Garden Decoration

Other Architectural Uses

Curbing

Industry

Construction Industry

As Dimension Stone, Building houses or walls, Cement Manufacture, for Road Aggregate, Roadstone

As Dimension Stone, Cement Manufacture, for Road Aggregate, Making natural cement

Medical Industry

Antiquity Uses

Artifacts

Artifacts, Monuments

Other Uses

Commercial Uses

Used in aquariums, Writing Slates

Creating Artwork, Gemstone

Types

Mica Schists, Calc-Silicate Schists, Graphite Schists, Blueschists, Whiteschists, Greenschists, Hornblende Schist, Talc Schist, Chlorite Schist, Garnet Schist, Glaucophane schist.

Cataclastic rock

Features

Easily splits into thin plates, Smooth to touch

Host Rock for Lead

Archaeological Significance

Monuments

Famous Monuments

Sculpture

Famous Sculptures

Pictographs

Petroglyphs

Figurines

Fossils

Absent

Formation

Schist formed by dynamic metamorphism at high temperatures and pressures that aligns the grains of mica, hornblende and other elongated minerals into thin layers.

Due to change in environmental conditions, rocks are heated and pressurized deep inside the Earth's surface. Pseudotachylite is formed from the extreme heat caused by magma or by the intense collisions and friction of tectonic plates.

Composition

Mineral Content

Alusite, Amphibole, Biotite, Chlorite, Epidote, Feldspar, Garnet, Graphite, Hornblade, Kyanite, Micas, Muscovite or Illite, Porphyroblasts, Quartz, Sillimanite, Staurolite, Talc

Iron Oxides, Pyroxene, Quartz, Stishovite, Sulfides

Compound Content

CaO, Carbon Dioxide, MgO

Carbon Dioxide, Silicon Dioxide, Sulfur Dioxide, Sulphur

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

3.5-47

1 7

👆🏻

Grain Size

Medium to Fine Coarse Grained

Very fine-grained

Fracture

Conchoidal

Uneven

Streak

White

Light to dark brown

Porosity

Highly Porous

Less Porous

Luster

Shiny

Vitreous

Compressive Strength

150.00 N/mm²60.00 N/mm²

0.15 450

👆🏻

Cleavage

Slaty

Toughness

1.5

Specific Gravity

2.5-2.92.46-2.86

0 8.4

👆🏻

Transparency

Opaque

Transparent to Translucent

Density

2.8-2.9 g/cm³2.7-2.9 g/cm³

0 1400

👆🏻

Thermal Properties

Specific Heat Capacity

0.70 kJ/Kg K0.92 kJ/Kg K

0.14 3.2

👆🏻

Resistance

Impact Resistant, Pressure Resistant, Water Resistant

Heat Resistant

Reserves

Deposits in Eastern Continents

Asia

Afghanistan, Bangladesh, Bhutan, China, India, Japan, Kazakhstan, Malaysia, Pakistan, Russia, Thailand, Turkey, Vietnam

South Korea

Africa

Egypt, Ethiopia, Morocco, Nigeria, South Africa

Western Africa

Europe

Austria, England, France, Georgia, Germany, Italy, Liechtenstein, Monaco, Norway, Slovenia, Spain, Sweden, Switzerland

Great Britain, Switzerland

Others

Deposits in Western Continents

North America

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

South America

Brazil, Colombia, Guyana

Deposits in Oceania Continent

Australia

New South Wales, New Zealand, Queensland

Central Australia, Western Australia

All about Schist and Pseudotachylite Properties

Know all about Schist and Pseudotachylite properties here. All properties of rocks are important as they define the type of rock and its application. Schist and Pseudotachylite belong to Metamorphic Rocks.Texture of Schist is Foliated, Platy whereas that of Pseudotachylite is Quench. Schist appears Layered and Shiny and Pseudotachylite appears Dull and Soft. The luster of Schist is shiny while that of Pseudotachylite is vitreous. Schist is available in black, blue, brown, dark brown, green, grey, silver colors whereas Pseudotachylite is available in black, brown, green, grey, pink, white colors. The commercial uses of Schist are used in aquariums, writing slates and that of Pseudotachylite are creating artwork, gemstone.