Chert and Picrite
Definition
Definition
Chert is a hard, dark, opaque sedimentary rock which is composed of silica with an amorphous fine-grained texture
Picrite is a variety of high-magnesium olivine basalt that is very rich in the mineral olivine
History
Origin
Unknown
Hawaii Islands
Discoverer
Unknown
Unknown
Etymology
From flint-like quartz, 1670s, of unknown origin- a local term, which has been taken into geological use
From Greek pikros bitter + -ite, 19th century
Class
Sedimentary Rocks
Igneous Rocks
Sub-Class
Durable Rock, Hard Rock
Durable Rock, Hard Rock
Family
Group
Not Applicable
Volcanic
Other Categories
Fine Grained Rock, Opaque Rock
Fine Grained Rock, Opaque Rock
Texture
Texture
Banded, Rough
Earthy, Rough
Color
Black, Brown, Green, Grey, Red, White
Black, Brown, Colourless, Green, Grey, Pink, White, Yellow
Maintenance
Less
Less
Durability
Durable
Durable
Water Resistant
Yes
Yes
Scratch Resistant
Yes
Yes
Stain Resistant
Yes
Yes
Wind Resistant
No
Yes
Acid Resistant
Yes
Yes
Appearance
Glassy or Pearly
Rough and Shiny
Uses
Architecture
Interior Uses
Decorative Aggregates, Homes
Countertops, Decorative Aggregates, Homes, Interior Decoration
Exterior Uses
As Building Stone, As Facing Stone, Garden Decoration, Office Buildings
As Building Stone, As Facing Stone, Garden Decoration, Paving Stone
Other Architectural Uses
Curbing
Curbing
Industry
Construction Industry
Arrowheads, Construction Aggregate, Cutting Tool, Spear Points
As a Sintering Agent in Steel Industry to process Iron Ore, Cement Manufacture, for Road Aggregate, Manufacture of Magnesium and Dolomite Refractories, Roadstone, Used for flooring, stair treads, borders and window sills.
Medical Industry
Not Yet Used
Not Yet Used
Antiquity Uses
Artifacts, Monuments
Artifacts, Monuments, Sculpture
Other Uses
Commercial Uses
Creating Artwork, Gemstone, In fire-starting tools, Jewelry, To ignite fire, Used in flintlock firearms
As a Feed Additive for Livestock, As armour rock for sea walls, Metallurgical Flux, Pottery, Source of Magnesia (MgO)
Types
Types
Flint, Jasper, Radiolarite, Common Chert, Chalcedony, Agate, Onyx, Opal, Magadi-type Chert, Porcelanite, Siliceous Sinter
Oceanite
Features
Clasts are smooth to touch, Easily splits into thin plates, Has High structural resistance against erosion and climate
Host Rock for Lead
Archaeological Significance
Monuments
Used
Used
Famous Monuments
Data Not Available
Data Not Available
Sculpture
Not Yet Used
Used
Famous Sculptures
Not Applicable
Data Not Available
Pictographs
Not Used
Not Used
Petroglyphs
Not Used
Not Used
Figurines
Not Yet Used
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.
Picrite is a fine-grained, hard rock which is a type of metasomatite, essentially altered basalt. It forms with or without crystallization, either below the surface as intrusive rocks or on the surface as extrusive rocks.
Composition
Mineral Content
Quartz, Silicon
Biotite, Olivine, Plagioclase, Pyrrhotite
Compound Content
Silicon Dioxide
Al, CaO, Carbon Dioxide, Mg, MgO
Transformation
Metamorphism
No
Yes
Types of Metamorphism
Not Applicable
Burial Metamorphism, Cataclastic Metamorphism, Impact Metamorphism, Regional Metamorphism
Weathering
No
Yes
Types of Weathering
Not Applicable
Biological Weathering
Erosion
Yes
Yes
Types of Erosion
Chemical Erosion
Chemical Erosion, Coastal Erosion, Glacier Erosion, Sea Erosion, Water Erosion, Wind Erosion
Properties
Physical Properties
Hardness
6.5-7
6.8
Grain Size
Very fine-grained
Fine Grained
Fracture
Uneven, Splintery or Conchoidal
Uneven
Streak
White
White, Greenish White or Grey
Porosity
Highly Porous
Less Porous
Luster
Waxy and Dull
Subvitreous to Dull
Compressive Strength
450.00 N/mm2
1
189.00 N/mm2
11
Cleavage
Non-Existent
Imperfect
Toughness
1.5
2.1
Specific Gravity
2.5-2.8
2.75-2.92
Transparency
Translucent to Opaque
Opaque
Density
2.7 g/cm3
1.5-2.5 g/cm3
Thermal Properties
Specific Heat Capacity
0.74 kJ/Kg K
19
0.88 kJ/Kg K
13
Resistance
Heat Resistant, Impact Resistant, Pressure Resistant, Wear Resistant
Heat Resistant
Reserves
Deposits in Eastern Continents
Asia
China, India, Iran, Japan, Oman, Russia, Saudi Arabia, Taiwan, Thailand, Vietnam
India, Russia
Africa
Kenya, Morocco, South Africa, Tanzania
South Africa
Europe
Austria, France, Greece, Italy, Malta, Poland, Portugal, Serbia, Spain, Sweden, United Kingdom
Iceland
Others
Greenland, Mid-Atlantic Ridge
Not Yet Found
Deposits in Western Continents
North America
Canada, Mexico, USA
Canada, USA
South America
Bolivia, Brazil
Brazil
Deposits in Oceania Continent
Australia
New South Wales, Queensland, South Australia, Western Australia
Not Yet Found
All about Chert and Picrite Properties
Know all about Chert and Picrite properties here. All properties of rocks are important as they define the type of rock and its application. Chert belongs to Sedimentary Rocks while Picrite belongs to Igneous Rocks.Texture of Chert is Banded, Rough whereas that of Picrite is Earthy, Rough. Chert appears Glassy or Pearly and Picrite appears Rough and Shiny. The luster of Chert is waxy and dull while that of Picrite is subvitreous to dull. Chert is available in black, brown, green, grey, red, white colors whereas Picrite is available in black, brown, colourless, green, grey, pink, white, 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 Picrite are as a feed additive for livestock, as armour rock for sea walls, metallurgical flux, pottery, source of magnesia (mgo).
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