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
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
Discoverer
Unknown
Obsius
Etymology
From the Middle High German verb gneist (to spark; so called because the rock glitters)
From Latin obsidianus, misprint of Obsianus (lapis) (stone) of Obsius
Class
Metamorphic Rocks
Igneous Rocks
Sub-Class
Durable Rock, Hard Rock
Durable Rock, Medium Hardness Rock
Other Categories
Coarse Grained Rock, Medium Grained Rock, Opaque Rock
Opaque Rock
Texture
Banded, Foliated, Platy
Glassy
Color
Black, Brown, Pink, Red, White
Black, Blue, Brown, Green, Orange, Red, Tan, Yellow
Durability
Durable
Durable
Scratch Resistant
Yes
Yes
Appearance
Foliated
Shiny
Interior Uses
Countertops, Decorative Aggregates, Flooring, Interior Decoration
Decorative Aggregates, Interior Decoration
Exterior Uses
As Building Stone, As Facing Stone, Garden Decoration, Paving Stone
Garden Decoration
Other Architectural Uses
Curbing
-
Construction Industry
As Dimension Stone
Arrowheads, Cutting Tool, Knives, Scrapers, Spear Points
Medical Industry
-
Surgery
Antiquity Uses
Artifacts
Artifacts, Jewellery
Commercial Uses
Cemetery Markers, Jewelry, Tombstones, Used in aquariums
Creating Artwork, Mirror, Used in aquariums
Types
Augen Gneiss, Henderson Gneiss, Lewisian Gneiss, Archean and Proterozoic Gneiss.
Fireworks Obsidian, Mahogany, Sheen Obsidian, Snowflake obsidian and Velvet Peacock Obsidian
Features
Generally rough to touch, Is one of the oldest rock
Blocks negativity, Helps to protect against depression
Archaeological Significance
Famous Monuments
Konark Sun Temple in India, Washington Monument, US
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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.
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.
Mineral Content
Biotite, Chlorite, Feldspar, Garnet, Graphite, Hornblade, Micas, Muscovite or Illite, Quartz, Quartzite, Silica, Zircon
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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
Types of Metamorphism
Impact Metamorphism
Burial Metamorphism, Cataclastic Metamorphism, Contact Metamorphism
Types of Weathering
Biological Weathering, Mechanical Weathering
Biological Weathering, Chemical Weathering, Mechanical Weathering
Types of Erosion
Chemical Erosion, Coastal Erosion, Sea Erosion
Chemical Erosion, Coastal Erosion, Glacier Erosion
Grain Size
Medium to Coarse Grained
-
Fracture
Irregular
Conchoidal
Porosity
Very Less Porous
Very Less Porous
Specific Gravity
2.5-2.7
2.6-2.7
Transparency
Translucent to Opaque
Translucent
Density
2.6-2.9 g/cm3
2.6 g/cm3
Resistance
Heat Resistant, Pressure Resistant, Scratch Resistant, Wear Resistant
Heat Resistant, Impact Resistant
Deposits in Eastern Continents
Asia
China, India, Iran, Iraq, Kazakhstan, Kyrgyzstan, Mongolia, Russia
Afghanistan, Indonesia, Japan, Russia
Africa
Cameroon, Ethiopia, Ghana, Kenya, Madagascar, Morocco, Mozambique, Namibia, Nigeria, Tanzania, Togo
Kenya
Europe
Albania, Austria, Bosnia and Herzegovina, Finland, France, Georgia, Germany, Hungary, Italy, Kosovo, Monaco, Norway, Poland, Romania, Serbia, Slovakia, Slovenia, Switzerland, Ukraine, United Kingdom
Greece, Hungary, Iceland, Italy, Turkey
Deposits in Western Continents
North America
Canada, Costa Rica, Cuba, Mexico, Panama, USA
Canada, Mexico, USA
South America
Argentina, Bolivia, Brazil, Chile, Colombia, Ecuador, Peru, Venezuela
Argentina, Chile, Ecuador, Peru
Deposits in Oceania Continent
Australia
New South Wales, New Zealand, Queensland, Victoria
New Zealand
Gneiss vs Obsidian 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. Gneiss vs Obsidian characteristics assist us to distinguish and recognize rocks. Also you can check about Properties of Gneiss and Properties of Obsidian. Learn more about Gneiss vs Obsidian in the next section. The interior uses of Gneiss include Countertops, Decorative aggregates, Flooring and Interior decoration whereas the interior uses of Obsidian include Decorative aggregates and Interior decoration. Due to some exceptional properties of Gneiss and Obsidian, they have various applications in construction industry. The uses of Gneiss in construction industry include As dimension stone and that of Obsidian include Arrowheads, Cutting tool, Knives, Scrapers, Spear points.
More about Gneiss and Obsidian
Here you can know more about Gneiss and Obsidian. The life cycle of a rock consists of formation of rock, composition of rock and transformation of rock. The composition of Gneiss and Obsidian consists of mineral content and compound content. The mineral content of Gneiss includes Biotite, Chlorite, Feldspar, Garnet, Graphite, Hornblade, Micas, Muscovite or Illite, Quartz, Quartzite, Silica, Zircon and mineral content of Obsidian includes . You can also check out the list of all Metamorphic Rocks. When we have to compare Gneiss vs Obsidian, the texture, color and appearance plays an important role in determining the type of rock. Gneiss is available in black, brown, pink, red, white colors whereas, Obsidian is available in black, blue, brown, green, orange, red, tan, yellow colors. Appearance of Gneiss is Foliated and that of Obsidian is Shiny. Properties of rock is another aspect for Gneiss vs Obsidian. The hardness of Gneiss is 7 and that of Obsidian is 5-5.5. The types of Gneiss are Augen Gneiss, Henderson Gneiss, Lewisian Gneiss, Archean and Proterozoic Gneiss. whereas types of Obsidian are Fireworks Obsidian, Mahogany, Sheen Obsidian, Snowflake obsidian and Velvet Peacock Obsidian. Streak of rock is the color of powder produced when it is dragged across an unweathered surface. The streak of Gneiss and Obsidian is white. The specific heat capacity of Gneiss is 0.70 kJ/Kg K and that of Obsidian is 0.92 kJ/Kg K. Depending on the properties like hardness, toughness, specific heat capacity, porosity etc., rocks are resistant to heat, wear, impact, etc.Gneiss is heat resistant, pressure resistant, scratch resistant, wear resistant whereas Obsidian is heat resistant, impact resistant.