Definition
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
Hornfels is a metamorphic rock formed by the contact between mudstone or other clay rich rock, and a hot igneous body, and represents a heat altered equivalent of the original rock
Origin
France
New Zealand
Discoverer
Unknown
Unknown
Etymology
From Latin varius, speckled, variegated
From German which means hornstone
Class
Igneous Rocks
Metamorphic Rocks
Sub-Class
Durable Rock, Hard Rock
Durable Rock, Soft Rock
Other Categories
Opaque Rock
Fine Grained Rock, Opaque Rock
Texture
Glassy, Massive, Porphyritic, Scoriaceous, Vesicular
Granular, Platy
Color
Black, Brown, Light to Dark Grey
Brown, Dark Greenish - Grey, Green, Reddish Brown
Durability
Durable
Durable
Appearance
Dull and Soft
Dull
Interior Uses
Floor Tiles, Flooring, Homes, Hotels, Kitchens
Decorative Aggregates, Flooring, Homes, Interior Decoration
Exterior Uses
Garden Decoration, Office Buildings
As Building Stone, As Facing Stone, Garden Decoration, Office Buildings, Paving Stone
Other Architectural Uses
Curbing
Curbing
Construction Industry
As Dimension Stone, Cobblestones, Rail Track Ballast, Roadstone
for Road Aggregate, Roadstone
Antiquity Uses
Artifacts, Monuments, Sculpture
Artifacts, Monuments
Commercial Uses
Cemetery Markers, Creating Artwork
Cemetery Markers, Commemorative Tablets, Creating Artwork
Types
Metamorphic rock
Biotite hornfels
Features
Has High structural resistance against erosion and climate, Very fine grained rock
Smooth to touch
Archaeological Significance
Formation
Variolites are a group of dark green basic igneous rocks that exhibit pale colored spots on weathered surfaces that give them a pockmarked appearance.
Due to change in environmental conditions, rocks are heated and pressurized deep inside the Earth's surface. Hornfels is formed from the extreme heat caused by magma or by the intense collisions and friction of tectonic plates.
Mineral Content
Olivine, Plagioclase, Pyroxene
Andalusite
Compound Content
Aluminium Oxide, CaO, Iron(III) Oxide, FeO, Potassium Oxide, MgO, MnO, Sodium Oxide, Phosphorus Pentoxide, Silicon Dioxide, Titanium Dioxide
Fe, Mg
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
Types of Erosion
-
Chemical Erosion, Glacier Erosion, Sea Erosion, Water Erosion, Wind Erosion
Grain Size
-
Fine Grained
Fracture
Conchoidal
Conchoidal
Porosity
Less Porous
Highly Porous
Specific Gravity
2.8-3
3.4-3.9
Transparency
Opaque
Opaque
Density
2.9-3.1 g/cm3
0.25-0.30 g/cm3
Resistance
Heat Resistant, Pressure Resistant, Wear Resistant
Heat Resistant, Impact Resistant, Pressure Resistant
Deposits in Eastern Continents
Asia
India, Russia
Bangladesh, Bhutan, China, India, North Korea, Qatar, Russia, Saudi Arabia, South Korea, Thailand
Africa
South Africa
Cameroon, East Africa, Tanzania, Western Africa
Europe
Iceland
United Kingdom
Deposits in Western Continents
North America
Canada, USA
Canada, USA
South America
Brazil
Bolivia, Brazil, Colombia, Ecuador
Deposits in Oceania Continent
Australia
-
New South Wales, New Zealand, Queensland, Western Australia
Variolite vs Hornfels 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. Variolite vs Hornfels characteristics assist us to distinguish and recognize rocks. Also you can check about Properties of Variolite and Properties of Hornfels. Learn more about Variolite vs Hornfels in the next section. The interior uses of Variolite include Floor tiles, Flooring, Homes, Hotels and Kitchens whereas the interior uses of Hornfels include Decorative aggregates, Flooring, Homes and Interior decoration. Due to some exceptional properties of Variolite and Hornfels, they have various applications in construction industry. The uses of Variolite in construction industry include As dimension stone, Cobblestones, Rail track ballast, Roadstone and that of Hornfels include For road aggregate, Roadstone.
More about Variolite and Hornfels
Here you can know more about Variolite and Hornfels. The life cycle of a rock consists of formation of rock, composition of rock and transformation of rock. The composition of Variolite and Hornfels consists of mineral content and compound content. The mineral content of Variolite includes Olivine, Plagioclase, Pyroxene and mineral content of Hornfels includes Andalusite. You can also check out the list of all Igneous Rocks. When we have to compare Variolite vs Hornfels, the texture, color and appearance plays an important role in determining the type of rock. Variolite is available in black, brown, light to dark grey colors whereas, Hornfels is available in brown, dark greenish - grey, green, reddish brown colors. Appearance of Variolite is Dull and Soft and that of Hornfels is Dull. Properties of rock is another aspect for Variolite vs Hornfels. The hardness of Variolite is 6 and that of Hornfels is 2-3. The types of Variolite are Metamorphic rock whereas types of Hornfels are Biotite hornfels. Streak of rock is the color of powder produced when it is dragged across an unweathered surface. The streak of Variolite is white to grey while that of Hornfels is . The specific heat capacity of Variolite is 0.84 kJ/Kg K and that of Hornfels 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.Variolite is heat resistant, pressure resistant, wear resistant whereas Hornfels is heat resistant, impact resistant, pressure resistant.