Chert and Obsidian
Definition
Definition
Chert is a hard, dark, opaque sedimentary rock which is composed of silica with an amorphous fine-grained texture
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
History
Origin
Unknown
Ethiopia
Discoverer
Unknown
Obsius
Etymology
From flint-like quartz, 1670s, of unknown origin- a local term, which has been taken into geological use
From Latin obsidianus, misprint of Obsianus (lapis) (stone) of Obsius
Class
Sedimentary Rocks
Igneous Rocks
Sub-Class
Durable Rock, Hard Rock
Durable Rock, Medium Hardness Rock
Family
Group
Not Applicable
Volcanic
Other Categories
Fine Grained Rock, Opaque Rock
Opaque Rock
Texture
Texture
Banded, Rough
Glassy
Color
Black, Brown, Green, Grey, Red, White
Black, Blue, Brown, Green, Orange, Red, Tan, Yellow
Maintenance
Less
Less
Durability
Durable
Durable
Water Resistant
Yes
Yes
Scratch Resistant
Yes
Yes
Stain Resistant
Yes
No
Wind Resistant
No
No
Acid Resistant
Yes
No
Appearance
Glassy or Pearly
Shiny
Uses
Architecture
Interior Uses
Decorative Aggregates, Homes
Decorative Aggregates, Interior Decoration
Exterior Uses
As Building Stone, As Facing Stone, Garden Decoration, Office Buildings
Garden Decoration
Other Architectural Uses
Curbing
Not Yet Used
Industry
Construction Industry
Arrowheads, Construction Aggregate, Cutting Tool, Spear Points
Arrowheads, Cutting Tool, Knives, Scrapers, Spear Points
Medical Industry
Not Yet Used
Surgery
Antiquity Uses
Artifacts, Monuments
Artifacts, Jewellery
Other Uses
Commercial Uses
Creating Artwork, Gemstone, In fire-starting tools, Jewelry, To ignite fire, Used in flintlock firearms
Creating Artwork, Mirror, Used in aquariums
Types
Types
Flint, Jasper, Radiolarite, Common Chert, Chalcedony, Agate, Onyx, Opal, Magadi-type Chert, Porcelanite, Siliceous Sinter
Fireworks Obsidian, Mahogany, Sheen Obsidian, Snowflake obsidian and Velvet Peacock Obsidian
Features
Clasts are smooth to touch, Easily splits into thin plates, Has High structural resistance against erosion and climate
Blocks negativity, Helps to protect against depression
Archaeological Significance
Monuments
Used
Not Yet Used
Famous Monuments
Data Not Available
Not Applicable
Sculpture
Not Yet Used
Not Yet Used
Famous Sculptures
Not Applicable
Not Applicable
Pictographs
Not Used
Used
Petroglyphs
Not Used
Used
Figurines
Not Yet Used
Not Yet Used
Fossils
Present
Absent
Formation
Formation
Chert forms when microcrystals of silicon dioxide grow within soft sediments that become limestone or chalk. The chert formation can be either of chemical or biological origin.
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.
Composition
Mineral Content
Quartz, Silicon
Not Available
Compound Content
Silicon Dioxide
Aluminium Oxide, CaO, Iron(III) Oxide, FeO, Potassium Oxide, MgO, MnO, Sodium Oxide, Phosphorus Pentoxide, Silicon Dioxide, Titanium Dioxide
Transformation
Metamorphism
No
Yes
Types of Metamorphism
Not Applicable
Burial Metamorphism, Cataclastic Metamorphism, Contact Metamorphism
Weathering
No
Yes
Types of Weathering
Not Applicable
Biological Weathering, Chemical Weathering, Mechanical Weathering
Erosion
Yes
Yes
Types of Erosion
Chemical Erosion
Chemical Erosion, Coastal Erosion, Glacier Erosion
Properties
Physical Properties
Hardness
6.5-7
5-5.5
Grain Size
Very fine-grained
Not Applicable
Fracture
Uneven, Splintery or Conchoidal
Conchoidal
Streak
White
White
Porosity
Highly Porous
Very Less Porous
Luster
Waxy and Dull
Vitreous
Compressive Strength
450.00 N/mm2
1
0.15 N/mm2
33
Cleavage
Non-Existent
Non-Existent
Toughness
1.5
Not Available
Specific Gravity
2.5-2.8
2.6-2.7
Transparency
Translucent to Opaque
Translucent
Density
2.7 g/cm3
2.6 g/cm3
Thermal Properties
Specific Heat Capacity
0.74 kJ/Kg K
19
0.92 kJ/Kg K
10
Resistance
Heat Resistant, Impact Resistant, Pressure Resistant, Wear Resistant
Heat Resistant, Impact Resistant
Reserves
Deposits in Eastern Continents
Asia
China, India, Iran, Japan, Oman, Russia, Saudi Arabia, Taiwan, Thailand, Vietnam
Afghanistan, Indonesia, Japan, Russia
Africa
Kenya, Morocco, South Africa, Tanzania
Kenya
Europe
Austria, France, Greece, Italy, Malta, Poland, Portugal, Serbia, Spain, Sweden, United Kingdom
Greece, Hungary, Iceland, Italy, Turkey
Others
Greenland, Mid-Atlantic Ridge
Not Yet Found
Deposits in Western Continents
North America
Canada, Mexico, USA
Canada, Mexico, USA
South America
Bolivia, Brazil
Argentina, Chile, Ecuador, Peru
Deposits in Oceania Continent
Australia
New South Wales, Queensland, South Australia, Western Australia
New Zealand
All about Chert and Obsidian Properties
Know all about Chert and Obsidian properties here. All properties of rocks are important as they define the type of rock and its application. Chert belongs to Sedimentary Rocks while Obsidian belongs to Igneous Rocks.Texture of Chert is Banded, Rough whereas that of Obsidian is Glassy. Chert appears Glassy or Pearly and Obsidian appears Shiny. The luster of Chert is waxy and dull while that of Obsidian is vitreous. Chert is available in black, brown, green, grey, red, white colors whereas Obsidian is available in black, blue, brown, green, orange, red, tan, yellow colors. The commercial uses of Chert are creating artwork, gemstone, in fire-starting tools, jewelry, to ignite fire, used in flintlock firearms and that of Obsidian are creating artwork, mirror, used in aquariums.
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