Hornfels

Variolite

Hornfels and Variolite

Hornfels

Variolite

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Definition

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

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

History

Origin

New Zealand

France

Discoverer

Unknown

Etymology

From German which means hornstone

From Latin varius, speckled, variegated

Class

Metamorphic Rocks

Igneous Rocks

Sub-Class

Durable Rock, Soft Rock

Durable Rock, Hard Rock

Family

Group

Volcanic

Other Categories

Fine Grained Rock, Opaque Rock

Opaque Rock

Texture

Granular, Platy

Glassy, Massive, Porphyritic, Scoriaceous, Vesicular

Color

Brown, Dark Greenish - Grey, Green, Reddish Brown

Black, Brown, Light to Dark Grey

Maintenance

Less

Durability

Durable

Water Resistant

✔ ✘

Scratch Resistant

✔ ✘

Stain Resistant

✔ ✘

Wind Resistant

✔ ✘

Acid Resistant

✔ ✘

Appearance

Dull

Dull and Soft

Uses

Architecture

Interior Uses

Decorative Aggregates, Flooring, Homes, Interior Decoration

Floor Tiles, Flooring, Homes, Hotels, Kitchens

Exterior Uses

As Building Stone, As Facing Stone, Garden Decoration, Office Buildings, Paving Stone

Garden Decoration, Office Buildings

Other Architectural Uses

Curbing

Industry

Construction Industry

for Road Aggregate, Roadstone

As Dimension Stone, Cobblestones, Rail Track Ballast, Roadstone

Medical Industry

Antiquity Uses

Artifacts, Monuments

Artifacts, Monuments, Sculpture

Other Uses

Commercial Uses

Cemetery Markers, Commemorative Tablets, Creating Artwork

Cemetery Markers, Creating Artwork

Types

Biotite hornfels

Metamorphic rock

Features

Smooth to touch

Has High structural resistance against erosion and climate, Very fine grained rock

Archaeological Significance

Monuments

Famous Monuments

Sculpture

Famous Sculptures

Pictographs

Petroglyphs

Figurines

Fossils

Absent

Formation

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.

Variolites are a group of dark green basic igneous rocks that exhibit pale colored spots on weathered surfaces that give them a pockmarked appearance.

Composition

Mineral Content

Andalusite

Olivine, Plagioclase, Pyroxene

Compound Content

Fe, Mg

Aluminium Oxide, CaO, Iron(III) Oxide, FeO, Potassium Oxide, MgO, MnO, Sodium Oxide, Phosphorus Pentoxide, Silicon Dioxide, Titanium Dioxide

Transformation

Metamorphism

✔ ✘

Types of Metamorphism

Burial Metamorphism, Cataclastic Metamorphism, Contact Metamorphism, Hydrothermal Metamorphism, Impact Metamorphism, Regional Metamorphism

Weathering

✔ ✘

Types of Weathering

Biological Weathering

Biological Weathering, Chemical Weathering, Mechanical Weathering

Erosion

✔ ✘

Types of Erosion

Chemical Erosion, Glacier Erosion, Sea Erosion, Water Erosion, Wind Erosion

Properties

Physical Properties

Hardness

2-36

1 7

👆🏻

Grain Size

Fine Grained

Fracture

Conchoidal

Streak

White to Grey

Porosity

Highly Porous

Less Porous

Luster

Shiny

Compressive Strength

5.80 N/mm²37.50 N/mm²

0.15 450

👆🏻

Cleavage

Perfect

Toughness

2.3

Specific Gravity

3.4-3.92.8-3

0 8.4

👆🏻

Transparency

Opaque

Density

0.25-0.30 g/cm³2.9-3.1 g/cm³

0 1400

👆🏻

Thermal Properties

Specific Heat Capacity

0.84 kJ/Kg K0.84 kJ/Kg K

0.14 3.2

👆🏻

Resistance

Heat Resistant, Impact Resistant, Pressure Resistant

Heat Resistant, Pressure Resistant, Wear Resistant

Reserves

Deposits in Eastern Continents

Asia

Bangladesh, Bhutan, China, India, North Korea, Qatar, Russia, Saudi Arabia, South Korea, Thailand

India, Russia

Africa

Cameroon, East Africa, Tanzania, Western Africa

South Africa

Europe

United Kingdom

Iceland

Others

Deposits in Western Continents

North America

Canada, USA

South America

Bolivia, Brazil, Colombia, Ecuador

Brazil

Deposits in Oceania Continent

Australia

New South Wales, New Zealand, Queensland, Western Australia

All about Hornfels and Variolite Properties

Know all about Hornfels and Variolite properties here. All properties of rocks are important as they define the type of rock and its application. Hornfels belongs to Metamorphic Rocks while Variolite belongs to Igneous Rocks.Texture of Hornfels is Granular, Platy whereas that of Variolite is Glassy, Massive, Porphyritic, Scoriaceous, Vesicular. Hornfels appears Dull and Variolite appears Dull and Soft. The luster of Hornfels is shiny while that of Variolite is . Hornfels is available in brown, dark greenish - grey, green, reddish brown colors whereas Variolite is available in black, brown, light to dark grey colors. The commercial uses of Hornfels and Variolite are cemetery markers, commemorative tablets, creating artwork.