Definition
Chalk is a soft, white, powdery limestone consisting mainly of fossil shells of foraminifers
  
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
  
History
  
  
Origin
Unknown
  
Ethiopia
  
Discoverer
Unknown
  
Obsius
  
Etymology
From old English cealc chalk, lime, plaster; pebble, from Greek khalix small pebble, in English transferred to the opaque, white, soft limestone
  
From Latin obsidianus, misprint of Obsianus (lapis) (stone) of Obsius
  
Class
Sedimentary Rocks
  
Igneous Rocks
  
Sub-Class
Durable Rock, Soft Rock
  
Durable Rock, Medium Hardness Rock
  
Family
  
  
Group
Not Applicable
  
Volcanic
  
Other Categories
Fine Grained Rock, Opaque Rock
  
Opaque Rock
  
Texture
Clastic or Non-Clastic
  
Glassy
  
Color
Grey, White, Yellow
  
Black, Blue, Brown, Green, Orange, Red, Tan, Yellow
  
Maintenance
Less
  
Less
  
Durability
Durable
  
Durable
  
Water Resistant
No
  
Yes
  
Scratch Resistant
No
  
Yes
  
Stain Resistant
No
  
No
  
Wind Resistant
No
  
No
  
Acid Resistant
No
  
No
  
Appearance
Soft
  
Shiny
  
Architecture
  
  
Interior Uses
Decorative Aggregates, Homes, Interior Decoration
  
Decorative Aggregates, Interior Decoration
  
Exterior Uses
As Building Stone, As Facing Stone, Paving Stone, Garden Decoration
  
Garden Decoration
  
Other Architectural Uses
Powder
  
Not Yet Used
  
Industry
  
  
Construction Industry
As Dimension Stone, Cement Manufacture, Construction Aggregate, for Road Aggregate, Making natural cement, raw material for manufacture of quicklime and slaked lime, Source of calcium
  
Arrowheads, Cutting Tool, Knives, Scrapers, Spear Points
  
Medical Industry
Not Yet Used
  
Surgery
  
Antiquity Uses
Artifacts, Monuments, Sculpture, Small Figurines
  
Artifacts, Jewellery
  
Other Uses
  
  
Commercial Uses
Alumina Refineries, Creating Artwork, Drawing on blackboards, Gymnasts, athletes and mountain climbers use for grip, In aquifers, Paper Industry, Production of Lime, Raw material for manufacture of quicklime, slaked lime, Soil Conditioner, Whiting, Whiting material in toothpaste, paint and paper
  
Creating Artwork, Mirror, Used in aquariums
  
Types
Not Available
  
Fireworks Obsidian, Mahogany, Sheen Obsidian, Snowflake obsidian and Velvet Peacock Obsidian
  
Features
Clasts are smooth to touch, Is one of the oldest rock, Smooth to touch, Very fine grained rock
  
Blocks negativity, Helps to protect against depression
  
Archaeological Significance
  
  
Monuments
Used
  
Not Yet Used
  
Famous Monuments
Data Not Available
  
Not Applicable
  
Sculpture
Used
  
Not Yet Used
  
Famous Sculptures
Data Not Available
  
Not Applicable
  
Pictographs
Used
  
Used
  
Petroglyphs
Used
  
Used
  
Figurines
Used
  
Not Yet Used
  
Fossils
Present
  
Absent
  
Formation
Chalk is formed from lime mud, which accumulates on the sea floor which is then transformed into rock by geological processes.
  
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.
  
Composition
  
  
Mineral Content
Calcite, Clay, Clay Minerals, Quartz, Sand
  
Not Available
  
Compound Content
Ca, NaCl, CaO
  
Aluminium Oxide, CaO, Iron(III) Oxide, FeO, Potassium Oxide, MgO, MnO, Sodium Oxide, Phosphorus Pentoxide, Silicon Dioxide, Titanium Dioxide
  
Transformation
  
  
Metamorphism
No
  
Yes
  
Types of Metamorphism
Not Applicable
  
Burial Metamorphism, Cataclastic Metamorphism, Contact Metamorphism
  
Weathering
Yes
  
Yes
  
Types of Weathering
Biological Weathering, Chemical Weathering
  
Biological Weathering, Chemical Weathering, Mechanical Weathering
  
Erosion
Yes
  
Yes
  
Types of Erosion
Chemical Erosion, Coastal Erosion, Water Erosion
  
Chemical Erosion, Coastal Erosion, Glacier Erosion
  
Physical Properties
  
  
Hardness
1
  
5-5.5
  
Grain Size
Very fine-grained
  
Not Applicable
  
Fracture
Not Available
  
Conchoidal
  
Streak
White
  
White
  
Porosity
Highly Porous
  
Very Less Porous
  
Luster
Dull
  
Vitreous
  
Compressive Strength
Not Available
  
Cleavage
Non-Existent
  
Non-Existent
  
Toughness
1
  
Not Available
  
Specific Gravity
2.3-2.4
  
2.6-2.7
  
Transparency
Opaque
  
Translucent
  
Density
2.49-2.50 g/cm3
  
2.6 g/cm3
  
Thermal Properties
  
  
Specific Heat Capacity
0.90 kJ/Kg K
  
12
0.92 kJ/Kg K
  
10
Resistance
Heat Resistant
  
Heat Resistant, Impact Resistant
  
Deposits in Eastern Continents
  
  
Asia
Brunei, India, Indonesia, Malaysia, Singapore, Thailand, Vietnam
  
Afghanistan, Indonesia, Japan, Russia
  
Africa
Cameroon, Chad, Ghana, Kenya, Malawi, Sudan, Tanzania, Togo, Zambia, Zimbabwe
  
Kenya
  
Europe
England, France, Germany, Spain, United Kingdom
  
Greece, Hungary, Iceland, Italy, Turkey
  
Others
Not Yet Found
  
Not Yet Found
  
Deposits in Western Continents
  
  
North America
Canada, USA
  
Canada, Mexico, USA
  
South America
Colombia
  
Argentina, Chile, Ecuador, Peru
  
Deposits in Oceania Continent
  
  
Australia
Adelaide, New Zealand, Queensland, Tonga, Victoria, Yorke Peninsula
  
New Zealand
  
All about Chalk and Obsidian Properties
Know all about Chalk and Obsidian properties here. All properties of rocks are important as they define the type of rock and its application. Chalk belongs to Sedimentary Rocks while Obsidian belongs to Igneous Rocks.Texture of Chalk is Clastic or Non-Clastic whereas that of Obsidian is Glassy. Chalk appears Soft and Obsidian appears Shiny. The luster of Chalk is dull while that of Obsidian is vitreous. Chalk is available in grey, white, yellow colors whereas Obsidian is available in black, blue, brown, green, orange, red, tan, yellow colors. The commercial uses of Chalk are alumina refineries, creating artwork, drawing on blackboards, gymnasts, athletes and mountain climbers use for grip, in aquifers, paper industry, production of lime, raw material for manufacture of quicklime, slaked lime, soil conditioner, whiting, whiting material in toothpaste, paint and paper and that of Obsidian are creating artwork, mirror, used in aquariums.