Porphyry

Picrite

Porphyry and Picrite

Porphyry

Picrite

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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

Picrite is a variety of high-magnesium olivine basalt that is very rich in the mineral olivine

History

Origin

Egypt

Hawaii Islands

Discoverer

Unknown

Etymology

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

From Greek pikros bitter + -ite, 19th century

Class

Igneous Rocks

Sub-Class

Durable Rock, Hard Rock

Family

Group

Plutonic

Volcanic

Other Categories

Fine Grained Rock, Opaque Rock

Texture

Porphyritic

Earthy, Rough

Color

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

Black, Brown, Green, Grey, Pink, White, Yellow

Maintenance

Less

Durability

Durable

Water Resistant

✔ ✘

Scratch Resistant

✔ ✘

Stain Resistant

✔ ✘

Wind Resistant

✔ ✘

Acid Resistant

✔ ✘

Appearance

Dull

Rough and Shiny

Uses

Architecture

Interior Uses

Decorative Aggregates, Interior Decoration

Countertops, Decorative Aggregates, Homes, Interior Decoration

Exterior Uses

Garden Decoration, Paving Stone

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

Other Architectural Uses

Curbing

Industry

Construction Industry

Construction Aggregate

As a Sintering Agent in Steel Industry to process Iron Ore, Cement Manufacture, for Road Aggregate, Manufacture of Magnesium and Dolomite Refractories, Roadstone, Used for flooring, stair treads, borders and window sills.

Medical Industry

Antiquity Uses

Artifacts, Monuments, Sculpture

Other Uses

Commercial Uses

Creating Artwork, Gemstone, Jewelry

As a Feed Additive for Livestock, As armour rock for sea walls, Metallurgical Flux, Pottery, Source of Magnesia (MgO)

Types

Rhomb Porphyry

Oceanite

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.

Picrite is a fine-grained, hard rock which is a type of metasomatite, essentially altered basalt. It forms with or without crystallization, either below the surface as intrusive rocks or on the surface as extrusive rocks.

Composition

Mineral Content

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

Biotite, Olivine, Plagioclase, Pyrrhotite

Compound Content

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

Al, CaO, Carbon Dioxide, Mg, MgO

Transformation

Metamorphism

✔ ✘

Types of Metamorphism

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

Burial Metamorphism, Cataclastic Metamorphism, Impact Metamorphism, Regional Metamorphism

Weathering

✔ ✘

Types of Weathering

Biological Weathering, Chemical Weathering

Biological Weathering

Erosion

✔ ✘

Types of Erosion

Chemical Erosion, Coastal Erosion, Glacier Erosion

Chemical Erosion, Coastal Erosion, Glacier Erosion, Sea Erosion, Water Erosion, Wind Erosion

Properties

Physical Properties

Hardness

6-76.8

1 7

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Grain Size

Fine Grained

Fracture

Irregular

Uneven

Streak

White

White, Greenish White or Grey

Porosity

Less Porous

Luster

Dull

Subvitreous to Dull

Compressive Strength

150.00 N/mm²189.00 N/mm²

0.15 450

👆🏻

Cleavage

Toughness

1.7

2.1

Specific Gravity

2.5-42.75-2.92

0 8.4

👆🏻

Transparency

Translucent to Opaque

Opaque

Density

2.5-2.52 g/cm³1.5-2.5 g/cm³

0 1400

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Thermal Properties

Specific Heat Capacity

0.71 kJ/Kg K0.88 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

India, Russia

Africa

Egypt, Ethiopia, Ghana, South Africa

South Africa

Europe

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

Iceland

Others

Greenland

Deposits in Western Continents

North America

Canada, Cuba, Jamaica, USA

Canada, USA

South America

Bolivia, Brazil, Colombia, Ecuador, Paraguay

Brazil

Deposits in Oceania Continent

Australia

New South Wales, New Zealand, Western Australia

All about Porphyry and Picrite Properties

Know all about Porphyry and Picrite properties here. All properties of rocks are important as they define the type of rock and its application. Porphyry and Picrite belong to Igneous Rocks.Texture of Porphyry is Porphyritic whereas that of Picrite is Earthy, Rough. Porphyry appears Dull and Picrite appears Rough and Shiny. The luster of Porphyry is dull while that of Picrite is subvitreous to dull. Porphyry is available in black, brown, green, grey, red, rust, white colors whereas Picrite is available in black, brown, green, grey, pink, white, yellow colors. The commercial uses of Porphyry are creating artwork, gemstone, jewelry and that of Picrite are as a feed additive for livestock, as armour rock for sea walls, metallurgical flux, pottery, source of magnesia (mgo).