Definition
Shale is a fine-grained sedimentary rock which is formed by the compaction of silt and clay-size mineral particles
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
Johann Gottlob Lehmann
Unknown
Etymology
From German Schalstein laminated limestone, and Schalgebirge layer of stone in stratified rock. From Old English scealu in its base sense of- thing that divides or separate,
From Latin varius, speckled, variegated
Class
Sedimentary Rocks
Igneous Rocks
Sub-Class
Durable Rock, Medium Hardness Rock
Durable Rock, Hard Rock
Other Categories
Fine Grained Rock, Opaque Rock
Opaque Rock
Texture
Clastic, Splintery
Glassy, Massive, Porphyritic, Scoriaceous, Vesicular
Color
Black, Brown, Buff, Green, Grey, Red, Yellow
Black, Brown, Light to Dark Grey
Durability
Durable
Durable
Appearance
Muddy
Dull and Soft
Interior Uses
Decorative Aggregates, Homes, Interior Decoration
Floor Tiles, Flooring, Homes, Hotels, Kitchens
Exterior Uses
As Building Stone, As Facing Stone, Office Buildings
Garden Decoration, Office Buildings
Other Architectural Uses
Curbing
Curbing
Construction Industry
Cement Manufacture, Construction Aggregate, for Road Aggregate, Making natural cement, Raw material for the manufacture of mortar
As Dimension Stone, Cobblestones, Rail Track Ballast, Roadstone
Antiquity Uses
Artifacts, Sculpture
Artifacts, Monuments, Sculpture
Commercial Uses
Creating Artwork, Pottery
Cemetery Markers, Creating Artwork
Types
Red Shale, Black Shale, Green Shale, Grey Shale and Yellow Shale
Metamorphic rock
Features
Easily splits into thin plates, Generally rough to touch, Very fine grained rock
Has High structural resistance against erosion and climate, Very fine grained rock
Archaeological Significance
Famous Monuments
Jantar Mantar in India
-
Formation
Shale forms when very fine-grained clay particles are deposited in water which settle at the bottom of water bodies. They are later compacted hence forming shale.
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
Albite, Biotite, Calcite, Chert, Chlorite, Dolomite, Hematite, Micas, Muscovite or Illite, Pyrite, Quartz, Silica, Sulfides
Olivine, Plagioclase, Pyroxene
Compound Content
Ca, Fe, Mg, Silicon Dioxide, Sodium
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, Contact Metamorphism, Hydrothermal Metamorphism, Impact Metamorphism, Regional Metamorphism
Types of Weathering
Biological Weathering, Chemical Weathering, Mechanical Weathering
Biological Weathering, Chemical Weathering, Mechanical Weathering
Types of Erosion
Chemical Erosion, Coastal Erosion, Glacier Erosion
-
Grain Size
Very fine-grained
-
Streak
White
White to Grey
Porosity
Highly Porous
Less Porous
Specific Gravity
2.2-2.8
2.8-3
Transparency
Opaque
Opaque
Density
2.4-2.8 g/cm3
2.9-3.1 g/cm3
Resistance
Heat Resistant, Impact Resistant
Heat Resistant, Pressure Resistant, Wear Resistant
Deposits in Eastern Continents
Asia
Bangladesh, China, India, Russia
India, Russia
Africa
Ethiopia, Kenya, Morocco, South Africa, Tanzania
South Africa
Europe
Austria, France, Germany, Greece, Italy, Romania, Scotland, Spain, Switzerland
Iceland
Deposits in Western Continents
North America
USA
Canada, USA
South America
Bolivia, Chile, Colombia, Ecuador, Peru, Venezuela
Brazil
Deposits in Oceania Continent
Australia
New South Wales, New Zealand, Queensland, Victoria, Western Australia
-
All about Shale and Variolite Properties
Know all about Shale and Variolite properties here. All properties of rocks are important as they define the type of rock and its application. Shale belongs to Sedimentary Rocks while Variolite belongs to Igneous Rocks.Texture of Shale is Clastic, Splintery whereas that of Variolite is Glassy, Massive, Porphyritic, Scoriaceous, Vesicular. Shale appears Muddy and Variolite appears Dull and Soft. The luster of Shale is dull while that of Variolite is . Shale is available in black, brown, buff, green, grey, red, yellow colors whereas Variolite is available in black, brown, light to dark grey colors. The commercial uses of Shale are creating artwork, pottery and that of Variolite are cemetery markers, creating artwork.