Definition
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
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
France
-
Discoverer
Unknown
Unknown
Etymology
From Latin varius, speckled, variegated
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
Durable Rock, Hard Rock
Family
Group
Volcanic
-
Other Categories
Opaque Rock
Coarse Grained Rock, Medium Grained Rock, Opaque Rock
Texture
Glassy, Massive, Porphyritic, Scoriaceous, Vesicular
Banded, Foliated, Platy
Color
Black, Brown, Light to Dark Grey
Black, Brown, Pink, Red, White
Maintenance
Less
More
Durability
Durable
Durable
Water Resistant
✔
✘
✔
✘
Scratch Resistant
✔
✘
✔
✘
Stain Resistant
✔
✘
✔
✘
Wind Resistant
✔
✘
✔
✘
Acid Resistant
✔
✘
✔
✘
Appearance
Dull and Soft
Foliated
Architecture
Interior Uses
Floor Tiles, Flooring, Homes, Hotels, Kitchens
Countertops, Decorative Aggregates, Flooring, Interior Decoration
Exterior Uses
Garden Decoration, Office Buildings
As Building Stone, As Facing Stone, Garden Decoration, Paving Stone
Other Architectural Uses
Curbing
Curbing
Industry
Construction Industry
As Dimension Stone, Cobblestones, Rail Track Ballast, Roadstone
As Dimension Stone
Medical Industry
-
-
Antiquity Uses
Artifacts, Monuments, Sculpture
Artifacts
Other Uses
Commercial Uses
Cemetery Markers, Creating Artwork
Cemetery Markers, Jewelry, Tombstones, Used in aquariums
Types
Metamorphic rock
Augen Gneiss, Henderson Gneiss, Lewisian Gneiss, Archean and Proterozoic Gneiss.
Features
Has High structural resistance against erosion and climate, Very fine grained rock
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
Absent
Formation
Variolites are a group of dark green basic igneous rocks that exhibit pale colored spots on weathered surfaces that give them a pockmarked appearance.
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
Olivine, Plagioclase, Pyroxene
Biotite, Chlorite, Feldspar, Garnet, Graphite, Hornblade, Micas, Muscovite or Illite, Quartz, Quartzite, Silica, Zircon
Compound Content
Aluminium Oxide, CaO, Iron(III) Oxide, FeO, Potassium Oxide, MgO, MnO, Sodium Oxide, Phosphorus Pentoxide, 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, Mechanical Weathering
Biological Weathering, Mechanical Weathering
Erosion
✔
✘
✔
✘
Types of Erosion
-
Chemical Erosion, Coastal Erosion, Sea Erosion
Physical Properties
Hardness
67
1
7
👆🏻
Grain Size
-
Medium to Coarse Grained
Fracture
Conchoidal
Irregular
Streak
White to Grey
White
Porosity
Less Porous
Very Less Porous
Luster
-
Dull
Compressive Strength
37.50 N/mm2125.00 N/mm2
0.15
450
👆🏻
Cleavage
-
-
Toughness
2.3
1.2
Specific Gravity
2.8-32.5-2.7
0
8.4
👆🏻
Transparency
Opaque
Translucent to Opaque
Density
2.9-3.1 g/cm32.6-2.9 g/cm3
0
1400
👆🏻
Thermal Properties
Specific Heat Capacity
0.84 kJ/Kg K0.70 kJ/Kg K
0.14
3.2
👆🏻
Resistance
Heat Resistant, Pressure Resistant, Wear Resistant
Heat Resistant, Pressure Resistant, Scratch Resistant, Wear Resistant
Deposits in Eastern Continents
Asia
India, Russia
China, India, Iran, Iraq, Kazakhstan, Kyrgyzstan, Mongolia, Russia
Africa
South Africa
Cameroon, Ethiopia, Ghana, Kenya, Madagascar, Morocco, Mozambique, Namibia, Nigeria, Tanzania, Togo
Europe
Iceland
Albania, Austria, Bosnia and Herzegovina, Finland, France, Georgia, Germany, Hungary, Italy, Kosovo, Monaco, Norway, Poland, Romania, Serbia, Slovakia, Slovenia, Switzerland, Ukraine, United Kingdom
Others
-
-
Deposits in Western Continents
North America
Canada, USA
Canada, Costa Rica, Cuba, Mexico, Panama, USA
South America
Brazil
Argentina, Bolivia, Brazil, Chile, Colombia, Ecuador, Peru, Venezuela
Deposits in Oceania Continent
Australia
-
New South Wales, New Zealand, Queensland, Victoria