Definition
Chert is a hard, dark, opaque sedimentary rock which is composed of silica with an amorphous fine-grained texture
  
Comendite is a hard, peralkaline igneous rock, a type of light blue grey rhyolite
  
History
  
  
Origin
Unknown
  
Italy
  
Discoverer
Unknown
  
Unknown
  
Etymology
From flint-like quartz, 1670s, of unknown origin- a local term, which has been taken into geological use
  
Comendite derives its name from the area of Le Commende on San Pietro Island in Italy
  
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
  
Medium Grained Rock, Opaque Rock
  
Texture
Banded, Rough
  
Porphyritic
  
Color
Black, Brown, Green, Grey, Red, White
  
Blue, Bluish - Grey
  
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
  
Foliated
  
Architecture
  
  
Interior Uses
Decorative Aggregates, Homes
  
Countertops, Decorative Aggregates, Interior Decoration
  
Exterior Uses
As Building Stone, As Facing Stone, Garden Decoration, Office Buildings
  
As Building Stone, As Facing Stone, Garden Decoration
  
Other Architectural Uses
Curbing
  
Curbing
  
Industry
  
  
Construction Industry
Arrowheads, Construction Aggregate, Cutting Tool, Spear Points
  
Building houses or walls, Cement Manufacture, Construction Aggregate, for Road Aggregate, Landscaping, Making natural cement, Raw material for the manufacture of mortar
  
Medical Industry
Not Yet Used
  
Not Yet Used
  
Antiquity Uses
Artifacts, Monuments
  
Artifacts
  
Other Uses
  
  
Commercial Uses
Creating Artwork, Gemstone, In fire-starting tools, Jewelry, To ignite fire, Used in flintlock firearms
  
Cemetery Markers
  
Types
Flint, Jasper, Radiolarite, Common Chert, Chalcedony, Agate, Onyx, Opal, Magadi-type Chert, Porcelanite, Siliceous Sinter
  
Rhyolite
  
Features
Clasts are smooth to touch, Easily splits into thin plates, Has High structural resistance against erosion and climate
  
Very fine grained rock, It is One of the Oldest, Strongest and Hardest Rock
  
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
  
Not Used
  
Petroglyphs
Not Used
  
Not Used
  
Figurines
Not Yet Used
  
Not Yet Used
  
Fossils
Present
  
Absent
  
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.
  
Comendite is a type of Igneous rock which is formed due to cooling and solidification of lava or magma. It may form with or without crystallization, either below the surface as intrusive rocks or on the surface as extrusive rocks.
  
Composition
  
  
Mineral Content
Quartz, Silicon
  
Albite, Amphibole, Quartz
  
Compound Content
Silicon Dioxide
  
Al, Fe, Potassium Oxide
  
Transformation
  
  
Metamorphism
No
  
Yes
  
Types of Metamorphism
Not Applicable
  
Cataclastic Metamorphism, Regional Metamorphism
  
Weathering
No
  
Yes
  
Types of Weathering
Not Applicable
  
Biological Weathering, Chemical Weathering, Mechanical Weathering
  
Erosion
Yes
  
Yes
  
Types of Erosion
Chemical Erosion
  
Coastal Erosion, Water Erosion
  
Physical Properties
  
  
Hardness
6.5-7
  
6-7
  
Grain Size
Very fine-grained
  
Medium Grained
  
Fracture
Uneven, Splintery or Conchoidal
  
Pervasive
  
Streak
White
  
Bluish Black
  
Porosity
Highly Porous
  
Highly Porous
  
Luster
Waxy and Dull
  
Dull
  
Compressive Strength
450.00 N/mm2
  
1
92.40 N/mm2
  
21
Cleavage
Non-Existent
  
Not Available
  
Toughness
1.5
  
2
  
Specific Gravity
2.5-2.8
  
2.38
  
Transparency
Translucent to Opaque
  
Opaque
  
Density
2.7 g/cm3
  
Not Available
  
Thermal Properties
  
  
Specific Heat Capacity
0.74 kJ/Kg K
  
19
Not Available
  
Resistance
Heat Resistant, Impact Resistant, Pressure Resistant, Wear Resistant
  
Heat Resistant, Impact Resistant
  
Deposits in Eastern Continents
  
  
Asia
China, India, Iran, Japan, Oman, Russia, Saudi Arabia, Taiwan, Thailand, Vietnam
  
China
  
Africa
Kenya, Morocco, South Africa, Tanzania
  
East Africa
  
Europe
Austria, France, Greece, Italy, Malta, Poland, Portugal, Serbia, Spain, Sweden, United Kingdom
  
Italy
  
Others
Greenland, Mid-Atlantic Ridge
  
Not Yet Found
  
Deposits in Western Continents
  
  
North America
Canada, Mexico, USA
  
Not Yet Found
  
South America
Bolivia, Brazil
  
Not Yet Found
  
Deposits in Oceania Continent
  
  
Australia
New South Wales, Queensland, South Australia, Western Australia
  
Queensland