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Obsidian and Hornfels


Hornfels and Obsidian


Definition

Definition
Obsidian is a naturally occurring volcanic glass formed as an extrusive igneous rock. It is produced when felsic lava extruded from a volcano cools rapidly with minimum crystal growth   
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   

History
  
  

Origin
Ethiopia   
New Zealand   

Discoverer
Obsius   
Unknown   

Etymology
From Latin obsidianus, misprint of Obsianus (lapis) (stone) of Obsius   
From German which means hornstone   

Class
Igneous Rocks   
Metamorphic Rocks   

Sub-Class
Durable Rock, Medium Hardness Rock   
Durable Rock, Soft Rock   

Family
  
  

Group
Volcanic   
Not Applicable   

Other Categories
Opaque Rock   
Fine Grained Rock, Opaque Rock   

Texture

Texture
Glassy   
Granular, Platy   

Color
Black, Blue, Brown, Green, Orange, Red, Tan, Yellow   
Brown, Dark Greenish - Grey, Green, Reddish Brown   

Maintenance
Less   
Less   

Durability
Durable   
Durable   

Water Resistant
Yes   
Yes   

Scratch Resistant
Yes   
No   

Stain Resistant
No   
No   

Wind Resistant
No   
No   

Acid Resistant
No   
No   

Appearance
Shiny   
Dull   

Uses

Architecture
  
  

Interior Uses
Decorative Aggregates, Interior Decoration   
Decorative Aggregates, Flooring, Homes, Interior Decoration   

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

Other Architectural Uses
Not Yet Used   
Curbing   

Industry
  
  

Construction Industry
Arrowheads, Cutting Tool, Knives, Scrapers, Spear Points   
for Road Aggregate, Roadstone   

Medical Industry
Surgery   
Not Yet Used   

Antiquity Uses
Artifacts, Jewellery   
Artifacts, Monuments   

Other Uses
  
  

Commercial Uses
Creating Artwork, Mirror, Used in aquariums   
Cemetery Markers, Commemorative Tablets, Creating Artwork   

Types

Types
Fireworks Obsidian, Mahogany, Sheen Obsidian, Snowflake obsidian and Velvet Peacock Obsidian   
Biotite hornfels   

Features
Blocks negativity, Helps to protect against depression   
Smooth to touch   

Archaeological Significance
  
  

Monuments
Not Yet Used   
Used   

Famous Monuments
Not Applicable   
Data Not Available   

Sculpture
Not Yet Used   
Not Yet Used   

Famous Sculptures
Not Applicable   
Not Applicable   

Pictographs
Used   
Used   

Petroglyphs
Used   
Used   

Figurines
Not Yet Used   
Not Yet Used   

Fossils
Absent   
Absent   

Formation

Formation
When the lava is released from volcano, it undergoes a very rapid cooling which freezes the mechanisms of crystallization. The result is a volcanic glass with a uniform smooth texture.   
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.   

Composition
  
  

Mineral Content
Not Available   
Andalusite   

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

Transformation
  
  

Metamorphism
Yes   
No   

Types of Metamorphism
Burial Metamorphism, Cataclastic Metamorphism, Contact Metamorphism   
Not Applicable   

Weathering
Yes   
Yes   

Types of Weathering
Biological Weathering, Chemical Weathering, Mechanical Weathering   
Biological Weathering   

Erosion
Yes   
Yes   

Types of Erosion
Chemical Erosion, Coastal Erosion, Glacier Erosion   
Chemical Erosion, Glacier Erosion, Sea Erosion, Water Erosion, Wind Erosion   

Properties

Physical Properties
  
  

Hardness
5-5.5   
2-3   

Grain Size
Not Applicable   
Fine Grained   

Fracture
Conchoidal   
Conchoidal   

Streak
White   
Unknown   

Porosity
Very Less Porous   
Highly Porous   

Luster
Vitreous   
Shiny   

Compressive Strength
0.15 N/mm2   
33
5.80 N/mm2   
31

Cleavage
Non-Existent   
Perfect   

Toughness
Not Available   
Not Yet Found   

Specific Gravity
2.6-2.7   
3.4-3.9   

Transparency
Translucent   
Opaque   

Density
2.6 g/cm3   
0.25-0.30 g/cm3   

Thermal Properties
  
  

Specific Heat Capacity
0.92 kJ/Kg K   
10
0.84 kJ/Kg K   
15

Resistance
Heat Resistant, Impact Resistant   
Heat Resistant, Impact Resistant, Pressure Resistant   

Reserves

Deposits in Eastern Continents
  
  

Asia
Afghanistan, Indonesia, Japan, Russia   
Bangladesh, Bhutan, China, India, North Korea, Qatar, Russia, Saudi Arabia, South Korea, Thailand   

Africa
Kenya   
Cameroon, East Africa, Tanzania, Western Africa   

Europe
Greece, Hungary, Iceland, Italy, Turkey   
United Kingdom   

Others
Not Yet Found   
Not Yet Found   

Deposits in Western Continents
  
  

North America
Canada, Mexico, USA   
Canada, USA   

South America
Argentina, Chile, Ecuador, Peru   
Bolivia, Brazil, Colombia, Ecuador   

Deposits in Oceania Continent
  
  

Australia
New Zealand   
New South Wales, New Zealand, Queensland, Western Australia   

Summary >>
<< Reserves

All about Obsidian and Hornfels Properties

Know all about Obsidian and Hornfels properties here. All properties of rocks are important as they define the type of rock and its application. Obsidian belongs to Igneous Rocks while Hornfels belongs to Metamorphic Rocks.Texture of Obsidian is Glassy whereas that of Hornfels is Granular, Platy. Obsidian appears Shiny and Hornfels appears Dull. The luster of Obsidian is vitreous while that of Hornfels is shiny. Obsidian is available in black, blue, brown, green, orange, red, tan, yellow colors whereas Hornfels is available in brown, dark greenish - grey, green, reddish brown colors. The commercial uses of Obsidian are creating artwork, mirror, used in aquariums and that of Hornfels are cemetery markers, commemorative tablets, creating artwork.

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