Definition
Coal is a combustible black or brownish-black sedimentary rock usually occurring in rock strata in layers called coal beds
Variolites are a group of dark green basic igneous rocks which exhibit pale colored spots, or spherules, especially on weathered surfaces, that give them a pockmarked appearance
Discoverer
John Peter Salley
Unknown
Etymology
From the Old English term col, which has meant mineral of fossilized carbon since the 13th century
From Latin varius, speckled, variegated
Class
Sedimentary Rocks
Igneous Rocks
Sub-Class
Durable Rock, Soft Rock
Durable Rock, Hard Rock
Group
Not Applicable
Volcanic
Other Categories
Coarse Grained Rock, Fine Grained Rock, Medium Grained Rock, Opaque Rock
Opaque Rock
Texture
Amorphous, Glassy
Glassy, Massive, Porphyritic, Scoriaceous, Vesicular
Color
Black, Brown, Dark Brown, Grey, Light to Dark Grey
Black, Brown, Light to Dark Grey
Durability
Durable
Durable
Appearance
Veined or Pebbled
Dull and Soft
Interior Uses
Not Yet Used
Floor Tiles, Flooring, Homes, Hotels, Kitchens
Exterior Uses
Not Yet Used
Garden Decoration, Office Buildings
Other Architectural Uses
Not Yet Used
Curbing
Construction Industry
Cement Manufacture, for Road Aggregate, Making natural cement, Steel Production
As Dimension Stone, Cobblestones, Rail Track Ballast, Roadstone
Medical Industry
Not Yet Used
Not Yet Used
Antiquity Uses
Artifacts
Artifacts, Monuments, Sculpture
Commercial Uses
Alumina Refineries, Electricity Generation, Liquid Fuel, Manufacture of Soap, Solvents, Dyes, Plastics and Fibres, Paper Industry
Cemetery Markers, Creating Artwork
Types
Peat, Lignite, Sub-Bituminous Coal, Bituminous Coal, Anthracite, Graphite
Not Available
Features
Helps in production of Heat and Electricity, Used as fossil fuel
Has High structural resistance against erosion and climate, Very fine grained rock
Archaeological Significance
Monuments
Not Yet Used
Used
Famous Monuments
Not Applicable
Data Not Available
Sculpture
Not Yet Used
Used
Famous Sculptures
Not Applicable
Data Not Available
Pictographs
Not Used
Used
Petroglyphs
Not Used
Used
Figurines
Not Yet Used
Used
Formation
Coal forms from the accumulation of plant debris in a swamp environment which is buried by sediments such as mud or sand and then compacted to form coal.
Variolites are a group of dark green basic igneous rocks that exhibit pale colored spots on weathered surfaces that give them a pockmarked appearance.
Mineral Content
Analcime, Apatite, Barite, Calcite, Chalcopyrite, Chlorite, Chromite, Clausthalite, Clay Minerals, Crandallite Group, Dolomite, Feldspar, Galena, Gypsum, Marcasite, Muscovite or Illite, Pyrite, Quartz, Siderite, Sphalerite, Zircon
Olivine, Plagioclase, Pyroxene
Compound Content
Carbon, Hydrogen, Nitrogen, Oxygen, Sulphur
Aluminium Oxide, CaO, Iron(III) Oxide, FeO, Potassium Oxide, MgO, MnO, Sodium Oxide, Phosphorus Pentoxide, Silicon Dioxide, Titanium Dioxide
Types of Metamorphism
Burial Metamorphism, Cataclastic Metamorphism, Regional Metamorphism
Burial Metamorphism, Cataclastic Metamorphism, Contact Metamorphism, Hydrothermal Metamorphism, Impact Metamorphism, Regional Metamorphism
Types of Weathering
Not Applicable
Biological Weathering, Chemical Weathering, Mechanical Weathering
Types of Erosion
Not Applicable
Not Applicable
Grain Size
Medium to Fine Coarse Grained
Not Applicable
Fracture
Conchoidal
Conchoidal
Streak
Black
White to Grey
Porosity
Less Porous
Less Porous
Luster
Dull to Vitreous to Submetallic
Not Available
Compressive Strength
Not Available
Cleavage
Non-Existent
Not Available
Toughness
Not Available
2.3
Specific Gravity
1.1-1.4
2.8-3
Transparency
Opaque
Opaque
Density
1100-1400 g/cm3
2.9-3.1 g/cm3
Resistance
Heat Resistant
Heat Resistant, Pressure Resistant, Wear Resistant
Deposits in Eastern Continents
Asia
Bangladesh, Burma, Cambodia, China, India, Indonesia, Kazakhstan, Malaysia, Mongolia, Pakistan, Turkey, Vietnam
India, Russia
Africa
Botswana, Kenya, Morocco, Mozambique, South Africa, Tanzania
South Africa
Europe
Belgium, Bulgaria, England, France, Germany, Greece, Hungary, Kosovo, Netherlands, Norway, Poland, Romania, Serbia, Slovakia, Slovenia, The Czech Republic, Ukraine, United Kingdom
Iceland
Others
Not Yet Found
Not Yet Found
Deposits in Western Continents
North America
Canada, Mexico, USA
Canada, USA
South America
Brazil, Chile, Colombia, Venezuela
Brazil
Deposits in Oceania Continent
Australia
New South Wales, Queensland, Victoria
Not Yet Found
Coal vs Variolite 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. Coal vs Variolite characteristics assist us to distinguish and recognize rocks. Also you can check about Properties of Coal and Properties of Variolite. Learn more about Coal vs Variolite in the next section. The interior uses of Coal include Not yet used whereas the interior uses of Variolite include Floor tiles, Flooring, Homes, Hotels and Kitchens. Due to some exceptional properties of Coal and Variolite, they have various applications in construction industry. The uses of Coal in construction industry include Cement manufacture, For road aggregate, Making natural cement, Steel production and that of Variolite include As dimension stone, Cobblestones, Rail track ballast, Roadstone.
More about Coal and Variolite
Here you can know more about Coal and Variolite. The life cycle of a rock consists of formation of rock, composition of rock and transformation of rock. The composition of Coal and Variolite consists of mineral content and compound content. The mineral content of Coal includes Analcime, Apatite, Barite, Calcite, Chalcopyrite, Chlorite, Chromite, Clausthalite, Clay Minerals, Crandallite Group, Dolomite, Feldspar, Galena, Gypsum, Marcasite, Muscovite or Illite, Pyrite, Quartz, Siderite, Sphalerite, Zircon and mineral content of Variolite includes Olivine, Plagioclase, Pyroxene. You can also check out the list of all Sedimentary Rocks. When we have to compare Coal vs Variolite, the texture, color and appearance plays an important role in determining the type of rock. Coal is available in black, brown, dark brown, grey, light to dark grey colors whereas, Variolite is available in black, brown, light to dark grey colors. Appearance of Coal is Veined or Pebbled and that of Variolite is Dull and Soft. Properties of rock is another aspect for Coal vs Variolite. The hardness of Coal is 1-1.5 and that of Variolite is 6. The types of Coal are Peat, Lignite, Sub-Bituminous Coal, Bituminous Coal, Anthracite, Graphite whereas types of Variolite are Not Available. Streak of rock is the color of powder produced when it is dragged across an unweathered surface. The streak of Coal is black while that of Variolite is white to grey. The specific heat capacity of Coal is 1.32 kJ/Kg K and that of Variolite is 0.84 kJ/Kg K. Depending on the properties like hardness, toughness, specific heat capacity, porosity etc., rocks are resistant to heat, wear, impact, etc.Coal is heat resistant whereas Variolite is heat resistant, pressure resistant, wear resistant.