Porphyry

Pseudotachylite

Porphyry and Pseudotachylite

Porphyry

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Definition

Porphyry is a reddish-brown to purple igneous rock containing large phenocrysts of various minerals embedded in a fine-grained matrix

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

History

Origin

Egypt

USA

Discoverer

Unknown

Etymology

From Old French porfire, from Italian porfiro and in some cases directly from Latin porphyrites

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

Class

Igneous Rocks

Metamorphic Rocks

Sub-Class

Durable Rock, Hard Rock

Family

Group

Plutonic

Other Categories

Fine Grained Rock, Opaque Rock

Texture

Porphyritic

Quench

Color

Black, Brown, Green, Grey, Red, Rust, White

Black, Brown, Green, Grey, Pink, White

Maintenance

Less

Durability

Durable

Water Resistant

✔ ✘

Scratch Resistant

✔ ✘

Stain Resistant

✔ ✘

Wind Resistant

✔ ✘

Acid Resistant

✔ ✘

Appearance

Dull

Dull and Soft

Uses

Architecture

Interior Uses

Decorative Aggregates, 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

Construction Aggregate

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

Medical Industry

Antiquity Uses

Artifacts, Monuments, Sculpture

Artifacts, Monuments

Other Uses

Commercial Uses

Creating Artwork, Gemstone, Jewelry

Creating Artwork, Gemstone

Types

Rhomb Porphyry

Cataclastic rock

Features

Generally rough to touch, Is one of the oldest rock, Surfaces are often shiny

Host Rock for Lead

Archaeological Significance

Monuments

Famous Monuments

Sculpture

Famous Sculptures

Pictographs

Petroglyphs

Figurines

Fossils

Absent

Formation

Porphyry is formed in two stages: the magma cools slowly deep within the crust or the magma is cools rapidly as it erupts from a volcano, creating small grains that are usually invisible to naked eye.

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

Biotite, Chert, Feldspar, Garnet, Graphite, Quartz, Silica

Iron Oxides, Pyroxene, Quartz, Stishovite, Sulfides

Compound Content

Aluminium Oxide, CaO, Iron(III) Oxide, Potassium Oxide, MgO, Sodium Oxide, Silicon Dioxide, Titanium Dioxide

Carbon Dioxide, Silicon Dioxide, Sulfur Dioxide, Sulphur

Transformation

Metamorphism

✔ ✘

Types of Metamorphism

Burial Metamorphism, Cataclastic Metamorphism, Contact Metamorphism, Hydrothermal Metamorphism, Impact Metamorphism, Regional Metamorphism

Burial Metamorphism, Cataclastic Metamorphism, Contact Metamorphism

Weathering

✔ ✘

Types of Weathering

Biological Weathering, Chemical Weathering

Erosion

✔ ✘

Types of Erosion

Chemical Erosion, Coastal Erosion, Glacier Erosion

Properties

Physical Properties

Hardness

6-77

1 7

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Grain Size

Fine Grained

Very fine-grained

Fracture

Irregular

Uneven

Streak

White

Light to dark brown

Porosity

Less Porous

Luster

Dull

Vitreous

Compressive Strength

150.00 N/mm²60.00 N/mm²

0.15 450

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Cleavage

Toughness

1.7

Specific Gravity

2.5-42.46-2.86

0 8.4

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Transparency

Translucent to Opaque

Transparent to Translucent

Density

2.5-2.52 g/cm³2.7-2.9 g/cm³

0 1400

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Thermal Properties

Specific Heat Capacity

0.71 kJ/Kg K0.92 kJ/Kg K

0.14 3.2

👆🏻

Resistance

Heat Resistant, Impact Resistant

Heat Resistant

Reserves

Deposits in Eastern Continents

Asia

China, Kazakhstan, South Korea, Thailand, Turkey, Vietnam

South Korea

Africa

Egypt, Ethiopia, Ghana, South Africa

Western Africa

Europe

Finland, France, Germany, Great Britain, Hungary, Iceland, Ireland, Italy, Netherlands, Norway, Romania, Sweden, Switzerland

Great Britain, Switzerland

Others

Greenland

Deposits in Western Continents

North America

Canada, Cuba, Jamaica, USA

South America

Bolivia, Brazil, Colombia, Ecuador, Paraguay

Deposits in Oceania Continent

Australia

New South Wales, New Zealand, Western Australia

Central Australia, Western Australia

All about Porphyry and Pseudotachylite Properties

Know all about Porphyry and Pseudotachylite properties here. All properties of rocks are important as they define the type of rock and its application. Porphyry belongs to Igneous Rocks while Pseudotachylite belongs to Metamorphic Rocks.Texture of Porphyry is Porphyritic whereas that of Pseudotachylite is Quench. Porphyry appears Dull and Pseudotachylite appears Dull and Soft. The luster of Porphyry is dull while that of Pseudotachylite is vitreous. Porphyry is available in black, brown, green, grey, red, rust, white colors whereas Pseudotachylite is available in black, brown, green, grey, pink, white colors. The commercial uses of Porphyry and Pseudotachylite are creating artwork, gemstone, jewelry.