Porphyry

Obsidian

Porphyry and Obsidian

Porphyry

Obsidian

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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

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

Egypt

Ethiopia

Discoverer

Unknown

Obsius

Etymology

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

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

Class

Igneous Rocks

Sub-Class

Durable Rock, Hard Rock

Durable Rock, Medium Hardness Rock

Family

Group

Plutonic

Volcanic

Other Categories

Fine Grained Rock, Opaque Rock

Opaque Rock

Texture

Porphyritic

Glassy

Color

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

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

Maintenance

Less

Durability

Durable

Water Resistant

✔ ✘

Scratch Resistant

✔ ✘

Stain Resistant

✔ ✘

Wind Resistant

✔ ✘

Acid Resistant

✔ ✘

Appearance

Dull

Shiny

Uses

Architecture

Interior Uses

Decorative Aggregates, Interior Decoration

Exterior Uses

Garden Decoration, Paving Stone

Garden Decoration

Other Architectural Uses

Curbing

Industry

Construction Industry

Construction Aggregate

Arrowheads, Cutting Tool, Knives, Scrapers, Spear Points

Medical Industry

Surgery

Antiquity Uses

Artifacts, Monuments, Sculpture

Artifacts, Jewellery

Other Uses

Commercial Uses

Creating Artwork, Gemstone, Jewelry

Creating Artwork, Mirror, Used in aquariums

Types

Rhomb Porphyry

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

Features

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

Blocks negativity, Helps to protect against depression

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.

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

Compound Content

Aluminium Oxide, CaO, Iron(III) Oxide, Potassium Oxide, MgO, Sodium Oxide, 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

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

Biological Weathering, Chemical Weathering, Mechanical Weathering

Erosion

✔ ✘

Types of Erosion

Chemical Erosion, Coastal Erosion, Glacier Erosion

Properties

Physical Properties

Hardness

6-75-5.5

1 7

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Grain Size

Fine Grained

Fracture

Irregular

Conchoidal

Streak

White

Porosity

Less Porous

Very Less Porous

Luster

Dull

Vitreous

Compressive Strength

150.00 N/mm²0.15 N/mm²

0.15 450

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Cleavage

Toughness

1.7

Specific Gravity

2.5-42.6-2.7

0 8.4

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Transparency

Translucent to Opaque

Translucent

Density

2.5-2.52 g/cm³2.6 g/cm³

0 1400

👆🏻

Thermal Properties

Specific Heat Capacity

0.71 kJ/Kg K0.92 kJ/Kg K

0.14 3.2

👆🏻

Resistance

Heat Resistant, Impact Resistant

Reserves

Deposits in Eastern Continents

Asia

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

Afghanistan, Indonesia, Japan, Russia

Africa

Egypt, Ethiopia, Ghana, South Africa

Kenya

Europe

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

Greece, Hungary, Iceland, Italy, Turkey

Others

Greenland

Deposits in Western Continents

North America

Canada, Cuba, Jamaica, USA

Canada, Mexico, USA

South America

Bolivia, Brazil, Colombia, Ecuador, Paraguay

Argentina, Chile, Ecuador, Peru

Deposits in Oceania Continent

Australia

New South Wales, New Zealand, Western Australia

New Zealand

All about Porphyry and Obsidian Properties

Know all about Porphyry and Obsidian properties here. All properties of rocks are important as they define the type of rock and its application. Porphyry and Obsidian belong to Igneous Rocks.Texture of Porphyry is Porphyritic whereas that of Obsidian is Glassy. Porphyry appears Dull and Obsidian appears Shiny. The luster of Porphyry is dull while that of Obsidian is vitreous. Porphyry is available in black, brown, green, grey, red, rust, white colors whereas Obsidian is available in black, blue, brown, green, orange, red, tan, yellow colors. The commercial uses of Porphyry are creating artwork, gemstone, jewelry and that of Obsidian are creating artwork, mirror, used in aquariums.