Gneiss and Variolite

Gneiss

Variolite

Definition

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

Variolites are a group of dark green basic igneous rocks which exhibit pale colored spots, or spherules, especially on weathered surfaces, that give them a pockmarked appearance

History

Origin

Unknown

France

Discoverer

Unknown

Etymology

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

From Latin varius, speckled, variegated

Class

Metamorphic Rocks

Igneous Rocks

Sub-Class

Durable Rock, Hard Rock

Family

Group

Not Applicable

Volcanic

Other Categories

Coarse Grained Rock, Medium Grained Rock, Opaque Rock

Opaque Rock

Texture

Banded, Foliated, Platy

Glassy, Massive, Porphyritic, Scoriaceous, Vesicular

Color

Black, Brown, Pink, Red, White

Black, Brown, Light to Dark Grey

Maintenance

Less

Durability

Durable

Water Resistant

Yes

Scratch Resistant

Yes

Stain Resistant

Yes

Wind Resistant

Yes

Acid Resistant

Yes

Appearance

Foliated

Dull and Soft

Uses

Architecture

Interior Uses

Countertops, Decorative Aggregates, Flooring, Interior Decoration

Floor Tiles, Flooring, Homes, Hotels, Kitchens

Exterior Uses

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

Garden Decoration, Office Buildings

Other Architectural Uses

Curbing

Industry

Construction Industry

As Dimension Stone

As Dimension Stone, Cobblestones, Rail Track Ballast, Roadstone

Medical Industry

Not Yet Used

Antiquity Uses

Artifacts

Artifacts, Monuments, Sculpture

Other Uses

Commercial Uses

Cemetery Markers, Jewelry, Tombstones, Used in aquariums

Cemetery Markers, Creating Artwork

Types

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

Not Available

Features

Generally rough to touch, Is one of the oldest rock

Has High structural resistance against erosion and climate, Very fine grained rock

Archaeological Significance

Monuments

Used

Famous Monuments

Konark Sun Temple in India, Washington Monument, US

Data Not Available

Sculpture

Not Yet Used

Used

Famous Sculptures

Not Applicable

Data Not Available

Pictographs

Not Used

Used

Petroglyphs

Not Used

Used

Figurines

Not Yet Used

Used

Fossils

Absent

Formation

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.

Variolites are a group of dark green basic igneous rocks that exhibit pale colored spots on weathered surfaces that give them a pockmarked appearance.

Composition

Mineral Content

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

Olivine, Plagioclase, Pyroxene

Compound Content

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

Yes

Types of Metamorphism

Impact Metamorphism

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

Weathering

Yes

Types of Weathering

Biological Weathering, Mechanical Weathering

Biological Weathering, Chemical Weathering, Mechanical Weathering

Erosion

Yes

Types of Erosion

Chemical Erosion, Coastal Erosion, Sea Erosion

Not Applicable

Properties

Physical Properties

Hardness

Grain Size

Medium to Coarse Grained

Not Applicable

Fracture

Irregular

Conchoidal

Streak

White

White to Grey

Porosity

Very Less Porous

Less Porous

Luster

Dull

Not Available

Compressive Strength

125.00 N/mm²

37.50 N/mm²

Cleavage

Poor

Not Available

Toughness

1.2

2.3

Specific Gravity

2.5-2.7

2.8-3

Transparency

Translucent to Opaque

Opaque

Density

2.6-2.9 g/cm³

2.9-3.1 g/cm³

Thermal Properties

Specific Heat Capacity

Not Available

0.84 kJ/Kg K

Resistance

Heat Resistant, Pressure Resistant, Scratch Resistant, Wear Resistant

Heat Resistant, Pressure Resistant, Wear Resistant

Reserves

Deposits in Eastern Continents

Asia

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

India, Russia

Africa

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

South Africa

Europe

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

Iceland

Others

Not Yet Found

Deposits in Western Continents

North America

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

Canada, USA

South America

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

Brazil

Deposits in Oceania Continent

Australia

New South Wales, New Zealand, Queensland, Victoria

Not Yet Found

Summary >>

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All about Gneiss and Variolite Properties

Know all about Gneiss and Variolite properties here. All properties of rocks are important as they define the type of rock and its application. Gneiss belongs to Metamorphic Rocks while Variolite belongs to Igneous Rocks.Texture of Gneiss is Banded, Foliated, Platy whereas that of Variolite is Glassy, Massive, Porphyritic, Scoriaceous, Vesicular. Gneiss appears Foliated and Variolite appears Dull and Soft. The luster of Gneiss is dull while that of Variolite is not available. Gneiss is available in black, brown, pink, red, white colors whereas Variolite is available in black, brown, light to dark grey colors. The commercial uses of Gneiss are cemetery markers, jewelry, tombstones, used in aquariums and that of Variolite are cemetery markers, creating artwork.