Definition
Nephelinite is a fine-grained or aphanitic igneous rock made up almost entirely of nepheline and clinopyroxene (variety augite).
  
Adakite is an intermediate to felsic volcanic rock that has geochemical characteristics of magma which is said to be formed by partial melting of altered basalt that is subducted below volcanic arcs
  
History
  
  
Origin
Brazil
  
Adak, Aleutian Islands
  
Discoverer
Unknown
  
Defant and Drummond
  
Etymology
from French néphéline, from Greek nephelē
  
From Adak, Aleutian Islands
  
Class
Igneous Rocks
  
Igneous Rocks
  
Sub-Class
Durable Rock, Hard Rock
  
Durable Rock, Medium Hardness Rock
  
Family
  
  
Group
Plutonic
  
Volcanic
  
Other Categories
Fine Grained Rock, Opaque Rock
  
Fine Grained Rock, Medium Grained Rock, Opaque Rock
  
Texture
Aphanitic
  
Porphyritic
  
Color
Black, Brown, Colourless, Green, Grey, White
  
Black, Brown, Light to Dark Grey
  
Maintenance
Less
  
Less
  
Durability
Durable
  
Durable
  
Water Resistant
Yes
  
No
  
Scratch Resistant
Yes
  
No
  
Stain Resistant
Yes
  
No
  
Wind Resistant
Yes
  
Yes
  
Acid Resistant
Yes
  
Yes
  
Appearance
Skeletal
  
Dull and Soft
  
Architecture
  
  
Interior Uses
Decorative Aggregates, Homes, Interior Decoration
  
Decorative Aggregates, Floor Tiles, Homes, Hotels, Kitchens
  
Exterior Uses
As Building Stone, As Facing Stone, Garden Decoration, Office Buildings, Paving Stone
  
As Building Stone, As Facing Stone, Office Buildings
  
Other Architectural Uses
Curbing
  
Whetstones
  
Industry
  
  
Construction Industry
As Dimension Stone, Cement Manufacture, Construction Aggregate, for Road Aggregate
  
As Dimension Stone, Cobblestones, Rail Track Ballast, Roadstone
  
Medical Industry
Not Yet Used
  
Not Yet Used
  
Antiquity Uses
Artifacts, Monuments, Sculpture, Small Figurines
  
Monuments, Sculpture, Small Figurines
  
Other Uses
  
  
Commercial Uses
Creating Artwork, Soil Conditioner, Source of Magnesia (MgO)
  
Commemorative Tablets, Pottery, Used in aquariums
  
Types
Peralkaline Nephelinite
  
Not Available
  
Features
Host Rock for Lead
  
Has High structural resistance against erosion and climate, Host rock for Diamond, Very fine grained rock
  
Archaeological Significance
  
  
Monuments
Used
  
Used
  
Famous Monuments
Data Not Available
  
Data Not Available
  
Sculpture
Used
  
Used
  
Famous Sculptures
Data Not Available
  
Data Not Available
  
Pictographs
Not Used
  
Used
  
Petroglyphs
Not Used
  
Used
  
Figurines
Used
  
Used
  
Fossils
Absent
  
Absent
  
Formation
Nephelinite is a fine-grained, hard rock which is a type of metasomatite, essentially altered basalt. It forms with or without crystallization, either below the surface as intrusive rocks or on the surface as extrusive rocks.
  
Adakite rocks are formed when the hydrous fluids are released from minerals that break down in metamorphosed basalt, and rise into the mantle they initiate partial melting.
  
Composition
  
  
Mineral Content
Clinopyroxene, Nepheline, Plagioclase
  
Olivine, Plagioclase, Pyroxene
  
Compound Content
Ca, CaO, Carbon, Cl, MgO
  
Aluminium Oxide, MgO, Silicon Dioxide
  
Transformation
  
  
Metamorphism
Yes
  
Yes
  
Types of Metamorphism
Contact Metamorphism
  
Cataclastic Metamorphism, Contact Metamorphism, Impact Metamorphism, Regional Metamorphism
  
Weathering
Yes
  
Yes
  
Types of Weathering
Biological Weathering, Chemical Weathering, Mechanical Weathering
  
Chemical Weathering, Mechanical Weathering
  
Erosion
Yes
  
Yes
  
Types of Erosion
Chemical Erosion, Water Erosion, Wind Erosion
  
Coastal Erosion, Sea Erosion, Water Erosion
  
Physical Properties
  
  
Hardness
6.5
  
3-4
  
Grain Size
Fine Grained
  
Fine to Medium Grained
  
Fracture
Flat
  
Conchoidal
  
Streak
White
  
Bluish Black
  
Porosity
Less Porous
  
Less Porous
  
Luster
Vitreous to Metallic
  
Grainy, Pearly and Vitreous
  
Compressive Strength
35.00 N/mm
2
  
29
Not Available
  
Cleavage
Imperfect
  
Not Available
  
Toughness
2.7
  
Not Available
  
Specific Gravity
2.4-2.9
  
Not Available
  
Transparency
Opaque
  
Opaque
  
Density
2.5-3 g/cm3
  
Not Available
  
Thermal Properties
  
  
Specific Heat Capacity
0.88 kJ/Kg K
  
13
Not Available
  
Resistance
Heat Resistant
  
Heat Resistant, Pressure Resistant, Wear Resistant
  
Deposits in Eastern Continents
  
  
Asia
Japan
  
India, Russia
  
Africa
Rwanda, Tanzania
  
Ethiopia, Somalia, South Africa
  
Europe
Not Yet Found
  
Iceland
  
Others
Hawaii Islands
  
Not Yet Found
  
Deposits in Western Continents
  
  
North America
Canada, USA
  
Canada, USA
  
South America
Colombia
  
Brazil
  
Deposits in Oceania Continent
  
  
Australia
Not Yet Found
  
Not Yet Found