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
Comendite is a hard, peralkaline igneous rock, a type of light blue grey rhyolite
History
Origin
Ethiopia
Italy
Discoverer
Obsius
Unknown
Etymology
From Latin obsidianus, misprint of Obsianus (lapis) (stone) of Obsius
Comendite derives its name from the area of Le Commende on San Pietro Island in Italy
Class
Igneous Rocks
Igneous Rocks
Sub-Class
Durable Rock, Medium Hardness Rock
Durable Rock, Hard Rock
Family
Group
Volcanic
Volcanic
Other Categories
Opaque Rock
Medium Grained Rock, Opaque Rock
Texture
Glassy
Porphyritic
Color
Black, Blue, Brown, Green, Orange, Red, Tan, Yellow
Blue, Bluish - Grey
Maintenance
Less
Less
Durability
Durable
Durable
Water Resistant
✔
✘
✔
✘
Scratch Resistant
✔
✘
✔
✘
Stain Resistant
✔
✘
✔
✘
Wind Resistant
✔
✘
✔
✘
Acid Resistant
✔
✘
✔
✘
Appearance
Shiny
Foliated
Architecture
Interior Uses
Decorative Aggregates, Interior Decoration
Countertops, Decorative Aggregates, Interior Decoration
Exterior Uses
Garden Decoration
As Building Stone, As Facing Stone, Garden Decoration
Other Architectural Uses
-
Curbing
Industry
Construction Industry
Arrowheads, Cutting Tool, Knives, Scrapers, Spear Points
Building houses or walls, Cement Manufacture, Construction Aggregate, for Road Aggregate, Landscaping, Making natural cement, Raw material for the manufacture of mortar
Medical Industry
Surgery
-
Antiquity Uses
Artifacts, Jewellery
Artifacts
Other Uses
Commercial Uses
Creating Artwork, Mirror, Used in aquariums
Cemetery Markers
Types
Fireworks Obsidian, Mahogany, Sheen Obsidian, Snowflake obsidian and Velvet Peacock Obsidian
Rhyolite
Features
Blocks negativity, Helps to protect against depression
Very fine grained rock, It is One of the Oldest, Strongest and Hardest Rock
Archaeological Significance
Monuments
-
-
Famous Monuments
-
-
Sculpture
-
-
Famous Sculptures
-
-
Pictographs
-
-
Petroglyphs
-
-
Figurines
-
-
Fossils
Absent
Absent
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.
Comendite is a type of Igneous rock which is formed due to cooling and solidification of lava or magma. It may form with or without crystallization, either below the surface as intrusive rocks or on the surface as extrusive rocks.
Composition
Mineral Content
-
Albite, Amphibole, Quartz
Compound Content
Aluminium Oxide, CaO, Iron(III) Oxide, FeO, Potassium Oxide, MgO, MnO, Sodium Oxide, Phosphorus Pentoxide, Silicon Dioxide, Titanium Dioxide
Al, Fe, Potassium Oxide
Transformation
Metamorphism
✔
✘
✔
✘
Types of Metamorphism
Burial Metamorphism, Cataclastic Metamorphism, Contact Metamorphism
Cataclastic Metamorphism, Regional Metamorphism
Weathering
✔
✘
✔
✘
Types of Weathering
Biological Weathering, Chemical Weathering, Mechanical Weathering
Biological Weathering, Chemical Weathering, Mechanical Weathering
Erosion
✔
✘
✔
✘
Types of Erosion
Chemical Erosion, Coastal Erosion, Glacier Erosion
Coastal Erosion, Water Erosion
Physical Properties
Hardness
5-5.56-7
1
7
👆🏻
Grain Size
-
Medium Grained
Fracture
Conchoidal
Pervasive
Streak
White
Bluish Black
Porosity
Very Less Porous
Highly Porous
Luster
Vitreous
Dull
Compressive Strength
0.15 N/mm292.40 N/mm2
0.15
450
👆🏻
Cleavage
-
-
Toughness
-
2
Specific Gravity
2.6-2.72.38
0
8.4
👆🏻
Transparency
Translucent
Opaque
Density
2.6 g/cm3-9999 g/cm3
0
1400
👆🏻
Thermal Properties
Specific Heat Capacity
0.92 kJ/Kg K0.79 kJ/Kg K
0.14
3.2
👆🏻
Resistance
Heat Resistant, Impact Resistant
Heat Resistant, Impact Resistant
Deposits in Eastern Continents
Asia
Afghanistan, Indonesia, Japan, Russia
China
Africa
Kenya
East Africa
Europe
Greece, Hungary, Iceland, Italy, Turkey
Italy
Others
-
-
Deposits in Western Continents
North America
Canada, Mexico, USA
-
South America
Argentina, Chile, Ecuador, Peru
-
Deposits in Oceania Continent
Australia
New Zealand
Queensland