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
  
Arkose is a sedimentary rock, specifically a type of sandstone containing at least 25% feldspar
  
History
  
  
Origin
Ethiopia
  
France
  
Discoverer
Obsius
  
Alexandre Brongniart
  
Etymology
From Latin obsidianus, misprint of Obsianus (lapis) (stone) of Obsius
  
From Auvergne region of France used by a French geologist Alexandre Brongniart in 1826 who applied this term to some feldspathic sandstones
  
Class
Igneous Rocks
  
Sedimentary Rocks
  
Sub-Class
Durable Rock, Medium Hardness Rock
  
Durable Rock, Hard Rock
  
Family
  
  
Group
Volcanic
  
Not Applicable
  
Other Categories
Opaque Rock
  
Coarse Grained Rock, Opaque Rock
  
Texture
Glassy
  
Clastic
  
Color
Black, Blue, Brown, Green, Orange, Red, Tan, Yellow
  
Reddish Brown
  
Maintenance
Less
  
Less
  
Durability
Durable
  
Durable
  
Water Resistant
Yes
  
Yes
  
Scratch Resistant
Yes
  
Yes
  
Stain Resistant
No
  
Yes
  
Wind Resistant
No
  
No
  
Acid Resistant
No
  
Yes
  
Appearance
Shiny
  
Rough and Dull
  
Architecture
  
  
Interior Uses
Decorative Aggregates, Interior Decoration
  
Decorative Aggregates, Homes, Interior Decoration
  
Exterior Uses
Garden Decoration
  
Paving Stone, Office Buildings
  
Other Architectural Uses
Not Yet Used
  
Whetstones
  
Industry
  
  
Construction Industry
Arrowheads, Cutting Tool, Knives, Scrapers, Spear Points
  
Cement Manufacture, Construction Aggregate, for Road Aggregate, Production of Glass and Ceramics, Raw material for the manufacture of mortar
  
Medical Industry
Surgery
  
Not Yet Used
  
Antiquity Uses
Artifacts, Jewellery
  
Artifacts, Sculpture, Small Figurines
  
Other Uses
  
  
Commercial Uses
Creating Artwork, Mirror, Used in aquariums
  
In aquifers, Soil Conditioner, Source of Magnesia (MgO), Tombstones
  
Types
Fireworks Obsidian, Mahogany, Sheen Obsidian, Snowflake obsidian and Velvet Peacock Obsidian
  
Not Available
  
Features
Blocks negativity, Helps to protect against depression
  
Available in Lots of Colors and Patterns, Generally rough to touch, Is one of the oldest rock
  
Archaeological Significance
  
  
Monuments
Not Yet Used
  
Not Yet Used
  
Famous Monuments
Not Applicable
  
Not Applicable
  
Sculpture
Not Yet Used
  
Used
  
Famous Sculptures
Not Applicable
  
Data Not Available
  
Pictographs
Used
  
Not Used
  
Petroglyphs
Used
  
Not Used
  
Figurines
Not Yet Used
  
Used
  
Fossils
Absent
  
Present
  
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.
  
Arkose rock forms from the weathering of feldspar-rich igneous or metamorphic rock, most commonly granitic rocks, which are primarily composed of quartz and feldspar.
  
Composition
  
  
Mineral Content
Not Available
  
Calcite, Clay, Clay Minerals, Feldspar, Micas, Quartz
  
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, Potassium Oxide, MgO, Sodium Oxide, Silicon Dioxide
  
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, Chemical Weathering, Mechanical Weathering
  
Erosion
Yes
  
Yes
  
Types of Erosion
Chemical Erosion, Coastal Erosion, Glacier Erosion
  
Coastal Erosion, Glacier Erosion, Water Erosion, Wind Erosion
  
Physical Properties
  
  
Hardness
5-5.5
  
6-7
  
Grain Size
Not Applicable
  
Coarse Grained
  
Fracture
Conchoidal
  
Conchoidal
  
Streak
White
  
White
  
Porosity
Very Less Porous
  
Highly Porous
  
Luster
Vitreous
  
Dull
  
Compressive Strength
Not Available
  
Cleavage
Non-Existent
  
Not Available
  
Toughness
Not Available
  
Not Available
  
Specific Gravity
2.6-2.7
  
0
  
Transparency
Translucent
  
Opaque
  
Density
2.6 g/cm3
  
Not Available
  
Thermal Properties
  
  
Specific Heat Capacity
0.92 kJ/Kg K
  
10
Not Available
  
Resistance
Heat Resistant, Impact Resistant
  
Heat Resistant, Impact Resistant, Pressure Resistant
  
Deposits in Eastern Continents
  
  
Asia
Afghanistan, Indonesia, Japan, Russia
  
China, India, Kazakhstan, Mongolia, Russia, Uzbekistan
  
Africa
Kenya
  
Namibia, Nigeria, South Africa
  
Europe
Greece, Hungary, Iceland, Italy, Turkey
  
Austria, Denmark, Germany, Great Britain, Netherlands, Norway, Poland, Sweden, Switzerland, United Kingdom
  
Others
Not Yet Found
  
Greenland
  
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
  
New South Wales, New Zealand