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
Mylonite is a metamorphic rock formed by ductile deformation during intense shearing encountered during folding and faulting, a process termed cataclastic or dynamic metamorphism
Origin
Ethiopia
New Zealand
Discoverer
Obsius
Unknown
Etymology
From Latin obsidianus, misprint of Obsianus (lapis) (stone) of Obsius
From Greek mulōn mill + -ite
Class
Igneous Rocks
Metamorphic Rocks
Sub-Class
Durable Rock, Medium Hardness Rock
Durable Rock, Medium Hardness Rock
Other Categories
Opaque Rock
Fine Grained Rock, Opaque Rock
Color
Black, Blue, Brown, Green, Orange, Red, Tan, Yellow
Black to Grey
Durability
Durable
Durable
Scratch Resistant
Yes
Yes
Appearance
Shiny
Dull, Banded and Foilated
Interior Uses
Decorative Aggregates, Interior Decoration
Decorative Aggregates, Interior Decoration
Exterior Uses
Garden Decoration
As Building Stone, As Facing Stone, Paving Stone, Garden Decoration
Other Architectural Uses
-
Curbing
Construction Industry
Arrowheads, Cutting Tool, Knives, Scrapers, Spear Points
for Road Aggregate, Landscaping, Roadstone
Medical Industry
Surgery
-
Antiquity Uses
Artifacts, Jewellery
Artifacts, Monuments
Commercial Uses
Creating Artwork, Mirror, Used in aquariums
Creating Artwork, Gemstone, Jewelry
Types
Fireworks Obsidian, Mahogany, Sheen Obsidian, Snowflake obsidian and Velvet Peacock Obsidian
Blastomylonites, Ultramylonites and Phyllonites
Features
Blocks negativity, Helps to protect against depression
Surfaces are often shiny
Archaeological Significance
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.
Mylonites are ductilely deformed rocks formed by the accumulation of large shear strain, in ductile fault zones.
Mineral Content
-
Porphyroblasts
Compound Content
Aluminium Oxide, CaO, Iron(III) Oxide, FeO, Potassium Oxide, MgO, MnO, Sodium Oxide, Phosphorus Pentoxide, Silicon Dioxide, Titanium Dioxide
Aluminium Oxide, Calcium Sulfate, Chromium(III) Oxide, Iron(III) Oxide, Magnesium Carbonate, Silicon Dioxide
Types of Metamorphism
Burial Metamorphism, Cataclastic Metamorphism, Contact 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
Chemical Erosion, Sea Erosion, Wind Erosion
Grain Size
-
Fine Grained
Fracture
Conchoidal
Conchoidal
Porosity
Very Less Porous
Highly Porous
Specific Gravity
2.6-2.7
2.97-3.05
Transparency
Translucent
Opaque
Density
2.6 g/cm3
2.6-4.8 g/cm3
Resistance
Heat Resistant, Impact Resistant
Heat Resistant, Impact Resistant, Pressure Resistant
Deposits in Eastern Continents
Asia
Afghanistan, Indonesia, Japan, Russia
China, India, Indonesia, Saudi Arabia, South Korea
Africa
Kenya
Eritrea, Ethiopia, Ghana, South Africa, Western Africa
Europe
Greece, Hungary, Iceland, Italy, Turkey
England, Finland, France, Germany, Great Britain, Greece, United Kingdom
Deposits in Western Continents
North America
Canada, Mexico, USA
USA
South America
Argentina, Chile, Ecuador, Peru
-
Deposits in Oceania Continent
Australia
New Zealand
Central Australia, Western Australia
All about Obsidian and Mylonite Properties
Know all about Obsidian and Mylonite properties here. All properties of rocks are important as they define the type of rock and its application. Obsidian belongs to Igneous Rocks while Mylonite belongs to Metamorphic Rocks.Texture of Obsidian is Glassy whereas that of Mylonite is Foliated. Obsidian appears Shiny and Mylonite appears Dull, Banded and Foilated. The luster of Obsidian is vitreous while that of Mylonite is shiny. Obsidian is available in black, blue, brown, green, orange, red, tan, yellow colors whereas Mylonite is available in black to grey colors. The commercial uses of Obsidian are creating artwork, mirror, used in aquariums and that of Mylonite are creating artwork, gemstone, jewelry.