Porphyry

Gneiss

Porphyry vs Gneiss

Porphyry

Gneiss

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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

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

History

Origin

Egypt

Discoverer

Unknown

Etymology

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

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

Class

Igneous Rocks

Metamorphic Rocks

Sub-Class

Durable Rock, Hard Rock

Family

Group

Plutonic

Other Categories

Fine Grained Rock, Opaque Rock

Coarse Grained Rock, Medium Grained Rock, Opaque Rock

Texture

Porphyritic

Banded, Foliated, Platy

Color

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

Black, Brown, Pink, Red, White

Maintenance

Less

Durability

Durable

Water Resistant

✔ ✘

Scratch Resistant

✔ ✘

Stain Resistant

✔ ✘

Wind Resistant

✔ ✘

Acid Resistant

✔ ✘

Appearance

Dull

Foliated

Uses

Architecture

Interior Uses

Decorative Aggregates, Interior Decoration

Countertops, Decorative Aggregates, Flooring, 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 Dimension Stone

Medical Industry

Antiquity Uses

Artifacts, Monuments, Sculpture

Artifacts

Other Uses

Commercial Uses

Creating Artwork, Gemstone, Jewelry

Cemetery Markers, Jewelry, Tombstones, Used in aquariums

Types

Rhomb Porphyry

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

Features

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

Generally rough to touch, Is one of the oldest rock

Archaeological Significance

Monuments

Famous Monuments

Konark Sun Temple in India, Washington Monument, US

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.

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.

Composition

Mineral Content

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

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

Compound Content

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

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

Transformation

Metamorphism

✔ ✘

Types of Metamorphism

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

Impact Metamorphism

Weathering

✔ ✘

Types of Weathering

Biological Weathering, Chemical Weathering

Biological Weathering, Mechanical Weathering

Erosion

✔ ✘

Types of Erosion

Chemical Erosion, Coastal Erosion, Glacier Erosion

Chemical Erosion, Coastal Erosion, Sea Erosion

Properties

Physical Properties

Hardness

6-77

1 7

👆🏻

Grain Size

Fine Grained

Medium to Coarse Grained

Fracture

Irregular

Streak

White

Porosity

Less Porous

Very Less Porous

Luster

Dull

Compressive Strength

150.00 N/mm²125.00 N/mm²

0.15 450

👆🏻

Cleavage

Toughness

1.7

1.2

Specific Gravity

2.5-42.5-2.7

0 8.4

👆🏻

Transparency

Translucent to Opaque

Density

2.5-2.52 g/cm³2.6-2.9 g/cm³

0 1400

👆🏻

Thermal Properties

Specific Heat Capacity

0.71 kJ/Kg K0.70 kJ/Kg K

0.14 3.2

👆🏻

Resistance

Heat Resistant, Impact Resistant

Heat Resistant, Pressure Resistant, Scratch Resistant, Wear Resistant

Reserves

Deposits in Eastern Continents

Asia

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

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

Africa

Egypt, Ethiopia, Ghana, South Africa

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

Europe

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

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

Others

Greenland

Deposits in Western Continents

North America

Canada, Cuba, Jamaica, USA

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

South America

Bolivia, Brazil, Colombia, Ecuador, Paraguay

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

Deposits in Oceania Continent

Australia

New South Wales, New Zealand, Western Australia

New South Wales, New Zealand, Queensland, Victoria

Porphyry vs Gneiss Information

Earth’s outer layer is covered by rocks and these rocks have different physical and chemical properties. As two rocks are not same, it’s fun to compare them. You can also know more about Porphyry and Gneiss Reserves. Porphyry is a reddish-brown to purple igneous rock containing large phenocrysts of various minerals embedded in a fine-grained matrix. 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. These rocks are composed of many distinct minerals. The process of formation of rocks is different for various rocks. Rocks are quarried from many years for various purposes. You can check out Porphyry vs Gneiss information and Porphyry vs Gneiss characteristics in the upcoming sections.

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Porphyry vs Gneiss Characteristics

Though some rocks look identical, they have certain characteristics which distinguish them from others. Characteristics of rocks include texture, appearance, color, fracture, streak, hardness etc. Porphyry vs Gneiss characteristics assist us to distinguish and recognize rocks. Also you can check about Properties of Porphyry and Properties of Gneiss. Learn more about Porphyry vs Gneiss in the next section. The interior uses of Porphyry include Decorative aggregates and Interior decoration whereas the interior uses of Gneiss include Countertops, Decorative aggregates, Flooring and Interior decoration. Due to some exceptional properties of Porphyry and Gneiss, they have various applications in construction industry. The uses of Porphyry in construction industry include Construction aggregate and that of Gneiss include As dimension stone.

More about Porphyry and Gneiss

Here you can know more about Porphyry and Gneiss. The life cycle of a rock consists of formation of rock, composition of rock and transformation of rock. The composition of Porphyry and Gneiss consists of mineral content and compound content. The mineral content of Porphyry includes Biotite, Chert, Feldspar, Garnet, Graphite, Quartz, Silica and mineral content of Gneiss includes Biotite, Chlorite, Feldspar, Garnet, Graphite, Hornblade, Micas, Muscovite or Illite, Quartz, Quartzite, Silica, Zircon. You can also check out the list of all Igneous Rocks. When we have to compare Porphyry vs Gneiss, the texture, color and appearance plays an important role in determining the type of rock. Porphyry is available in black, brown, green, grey, red, rust, white colors whereas, Gneiss is available in black, brown, pink, red, white colors. Appearance of Porphyry is Dull and that of Gneiss is Foliated. Properties of rock is another aspect for Porphyry vs Gneiss. The hardness of Porphyry is 6-7 and that of Gneiss is 7. The types of Porphyry are Rhomb Porphyry whereas types of Gneiss are Augen Gneiss, Henderson Gneiss, Lewisian Gneiss, Archean and Proterozoic Gneiss.. Streak of rock is the color of powder produced when it is dragged across an unweathered surface. The streak of Porphyry and Gneiss is white. The specific heat capacity of Porphyry is 0.71 kJ/Kg K and that of Gneiss is 0.70 kJ/Kg K. Depending on the properties like hardness, toughness, specific heat capacity, porosity etc., rocks are resistant to heat, wear, impact, etc.Porphyry is heat resistant, impact resistant whereas Gneiss is heat resistant, pressure resistant, scratch resistant, wear resistant.