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
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
Ethiopia
France
Discoverer
Obsius
Unknown
Etymology
From Latin obsidianus, misprint of Obsianus (lapis) (stone) of Obsius
From Latin varius, speckled, variegated
Class
Igneous Rocks
Igneous Rocks
Sub-Class
Durable Rock, Medium Hardness Rock
Durable Rock, Hard Rock
Family
Group
Volcanic
Volcanic
Other Categories
Opaque Rock
Opaque Rock
Texture
Glassy
Glassy, Massive, Porphyritic, Scoriaceous, Vesicular
Color
Black, Blue, Brown, Green, Orange, Red, Tan, Yellow
Black, Brown, Light to Dark Grey
Maintenance
Less
Less
Durability
Durable
Durable
Water Resistant
✔
✘
✔
✘
Scratch Resistant
✔
✘
✔
✘
Stain Resistant
✔
✘
✔
✘
Wind Resistant
✔
✘
✔
✘
Acid Resistant
✔
✘
✔
✘
Appearance
Shiny
Dull and Soft
Architecture
Interior Uses
Decorative Aggregates, Interior Decoration
Floor Tiles, Flooring, Homes, Hotels, Kitchens
Exterior Uses
Garden Decoration
Garden Decoration, Office Buildings
Other Architectural Uses
-
Curbing
Industry
Construction Industry
Arrowheads, Cutting Tool, Knives, Scrapers, Spear Points
As Dimension Stone, Cobblestones, Rail Track Ballast, Roadstone
Medical Industry
Surgery
-
Antiquity Uses
Artifacts, Jewellery
Artifacts, Monuments, Sculpture
Other Uses
Commercial Uses
Creating Artwork, Mirror, Used in aquariums
Cemetery Markers, Creating Artwork
Types
Fireworks Obsidian, Mahogany, Sheen Obsidian, Snowflake obsidian and Velvet Peacock Obsidian
Metamorphic rock
Features
Blocks negativity, Helps to protect against depression
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
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.
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
-
Olivine, Plagioclase, Pyroxene
Compound Content
Aluminium Oxide, CaO, Iron(III) Oxide, FeO, Potassium Oxide, MgO, MnO, Sodium Oxide, Phosphorus Pentoxide, Silicon Dioxide, Titanium Dioxide
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
Burial Metamorphism, Cataclastic Metamorphism, Contact Metamorphism, Hydrothermal Metamorphism, Impact 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
-
Physical Properties
Hardness
5-5.56
1
7
👆🏻
Grain Size
-
-
Fracture
Conchoidal
Conchoidal
Streak
White
White to Grey
Porosity
Very Less Porous
Less Porous
Luster
Vitreous
-
Compressive Strength
0.15 N/mm237.50 N/mm2
0.15
450
👆🏻
Cleavage
-
-
Toughness
-
2.3
Specific Gravity
2.6-2.72.8-3
0
8.4
👆🏻
Transparency
Translucent
Opaque
Density
2.6 g/cm32.9-3.1 g/cm3
0
1400
👆🏻
Thermal Properties
Specific Heat Capacity
0.92 kJ/Kg K0.84 kJ/Kg K
0.14
3.2
👆🏻
Resistance
Heat Resistant, Impact Resistant
Heat Resistant, Pressure Resistant, Wear Resistant
Deposits in Eastern Continents
Asia
Afghanistan, Indonesia, Japan, Russia
India, Russia
Africa
Kenya
South Africa
Europe
Greece, Hungary, Iceland, Italy, Turkey
Iceland
Others
-
-
Deposits in Western Continents
North America
Canada, Mexico, USA
Canada, USA
South America
Argentina, Chile, Ecuador, Peru
Brazil
Deposits in Oceania Continent
Australia
New Zealand
-