Definition
Andesite is a dark, fine-grained, brown or greyish intermediate volcanic rock which is a commonly found in lava
Chert is a hard, dark, opaque sedimentary rock which is composed of silica with an amorphous fine-grained texture
Discoverer
Theodor von Gümbel
Unknown
Etymology
From Andes mountains, where it is found in abundance
From flint-like quartz, 1670s, of unknown origin- a local term, which has been taken into geological use
Class
Igneous Rocks
Sedimentary Rocks
Sub-Class
Durable Rock, Hard Rock
Durable Rock, Hard Rock
Other Categories
Fine Grained Rock, Opaque Rock
Fine Grained Rock, Opaque Rock
Texture
Aphanitic to Porphyritic
Banded, Rough
Color
Bluish - Grey, Grey, Pink, Yellow
Black, Brown, Green, Grey, Red, White
Durability
Durable
Durable
Scratch Resistant
Yes
Yes
Appearance
Dull and Soft
Glassy or Pearly
Interior Uses
Decorative Aggregates, Floor Tiles, Homes, Interior Decoration, Kitchens
Decorative Aggregates, Homes
Exterior Uses
Office Buildings, Roof Tiles
As Building Stone, As Facing Stone, Garden Decoration, Office Buildings
Other Architectural Uses
Curbing
Curbing
Construction Industry
Cobblestones, Construction Aggregate, for Road Aggregate
Arrowheads, Construction Aggregate, Cutting Tool, Spear Points
Antiquity Uses
Artifacts, Monuments, Sculpture, Small Figurines
Artifacts, Monuments
Commercial Uses
Commemorative Tablets, Creating Artwork
Creating Artwork, Gemstone, In fire-starting tools, Jewelry, To ignite fire, Used in flintlock firearms
Types
Icelandite
Flint, Jasper, Radiolarite, Common Chert, Chalcedony, Agate, Onyx, Opal, Magadi-type Chert, Porcelanite, Siliceous Sinter
Features
Generally rough to touch, High silica content, Is one of the oldest rock
Clasts are smooth to touch, Easily splits into thin plates, Has High structural resistance against erosion and climate
Archaeological Significance
Famous Monuments
Middle of the Earth in Ecuador
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Formation
Andesite is a fine-grained igneous rock that forms when the magma is erupted onto the surface and is crystallized quickly.
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.
Mineral Content
Amphibole, Apatite, Biotite, Feldspar, Garnet, Hornblade, Ilmenite, Magnetite, Plagioclase, Pyroxene, Zircon
Quartz, Silicon
Compound Content
Silicon Dioxide
Silicon Dioxide
Types of Metamorphism
Burial Metamorphism, Cataclastic Metamorphism, Contact Metamorphism, Hydrothermal Metamorphism, Impact Metamorphism, Regional Metamorphism
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Types of Weathering
Biological Weathering, Chemical Weathering, Mechanical Weathering
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Types of Erosion
Chemical Erosion, Coastal Erosion, Glacier Erosion
Chemical Erosion
Grain Size
Very fine-grained
Very fine-grained
Fracture
Uneven
Uneven, Splintery or Conchoidal
Porosity
Less Porous
Highly Porous
Luster
Vitreous
Waxy and Dull
Specific Gravity
2.5-2.8
2.5-2.8
Transparency
Opaque
Translucent to Opaque
Density
2.11-2.36 g/cm3
2.7 g/cm3
Resistance
Heat Resistant, Pressure Resistant, Wear Resistant
Heat Resistant, Impact Resistant, Pressure Resistant, Wear Resistant
Deposits in Eastern Continents
Asia
India, Indonesia, Japan, Nepal, South Korea
China, India, Iran, Japan, Oman, Russia, Saudi Arabia, Taiwan, Thailand, Vietnam
Africa
Egypt, Ethiopia, Morocco, Namibia, South Africa, Tanzania
Kenya, Morocco, South Africa, Tanzania
Europe
Austria, Finland, Germany, Italy, Romania, Turkey, United Kingdom
Austria, France, Greece, Italy, Malta, Poland, Portugal, Serbia, Spain, Sweden, United Kingdom
Others
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Greenland, Mid-Atlantic Ridge
Deposits in Western Continents
North America
Mexico, USA
Canada, Mexico, USA
South America
Argentina, Bolivia, Chile, Colombia, Ecuador, Peru, Venezuela
Bolivia, Brazil
Deposits in Oceania Continent
Australia
New South Wales, New Zealand, Western Australia
New South Wales, Queensland, South Australia, Western Australia