Definition
Schist is a medium grade metamorphic rock with medium to large, flat, sheet like grains in a preferred orientation
Trachyte is a grey fine-grained volcanic rock which mainly consists of alkali feldspar
Discoverer
Unknown
Alexandre Brongniart and René Just Haüy
Etymology
From French schiste, Greek skhistos i.e. split
From Greek trakhus rough’ or trakhutēs roughness
Class
Metamorphic Rocks
Igneous Rocks
Sub-Class
Durable Rock, Medium Hardness Rock
Durable Rock, Medium Hardness Rock
Other Categories
Coarse Grained Rock, Fine Grained Rock, Medium Grained Rock, Opaque Rock
Fine Grained Rock, Opaque Rock
Texture
Foliated, Platy
Aphanitic to Porphyritic
Color
Black, Blue, Brown, Dark Brown, Green, Grey, Silver
Black, Brown, Dark Greenish - Grey, Green, Grey, Light to Dark Grey, White
Durability
Durable
Durable
Appearance
Layered and Shiny
Banded
Interior Uses
Decorative Aggregates, Floor Tiles, Interior Decoration
Decorative Aggregates, Flooring, Homes, Interior Decoration
Exterior Uses
Garden Decoration, Paving Stone
As Building Stone, As Facing Stone, Paving Stone, Garden Decoration, Office Buildings
Other Architectural Uses
-
Curbing
Construction Industry
As Dimension Stone, Building houses or walls, Cement Manufacture, for Road Aggregate, Roadstone
As Dimension Stone, Building houses or walls, Cement Manufacture, Construction Aggregate, for Road Aggregate, Landscaping, Making natural cement, Manufacture of Magnesium and Dolomite Refractories
Antiquity Uses
Artifacts
Artifacts, Monuments, Sculpture, Small Figurines
Commercial Uses
Used in aquariums, Writing Slates
Cemetery Markers, Creating Artwork
Types
Mica Schists, Calc-Silicate Schists, Graphite Schists, Blueschists, Whiteschists, Greenschists, Hornblende Schist, Talc Schist, Chlorite Schist, Garnet Schist, Glaucophane schist.
Felsic volcanic rock
Features
Easily splits into thin plates, Smooth to touch
Available in Lots of Colors and Patterns, Is one of the oldest rock, Matrix variable
Archaeological Significance
Formation
Schist formed by dynamic metamorphism at high temperatures and pressures that aligns the grains of mica, hornblende and other elongated minerals into thin layers.
Trachyte is an igneous volcanic rock with an aphanitic to porphyritic texture. It is the volcanic equivalent of syenite rock and forms as a result of magmatic differentiation.
Mineral Content
Alusite, Amphibole, Biotite, Chlorite, Epidote, Feldspar, Garnet, Graphite, Hornblade, Kyanite, Micas, Muscovite or Illite, Porphyroblasts, Quartz, Sillimanite, Staurolite, Talc
Augite, Biotite, Feldspar, Hornblade, Plagioclase, Quartz
Compound Content
CaO, Carbon Dioxide, MgO
Potassium Oxide, Sodium Oxide, Silicon Dioxide
Types of Metamorphism
-
Cataclastic Metamorphism, Contact Metamorphism, Regional Metamorphism
Types of Weathering
Biological Weathering, Chemical Weathering, Mechanical Weathering
Biological Weathering, Chemical Weathering, Mechanical Weathering
Types of Erosion
Chemical Erosion, Coastal Erosion, Glacier Erosion
Chemical Erosion, Coastal Erosion, Glacier Erosion, Sea Erosion, Water Erosion, Wind Erosion
Grain Size
Medium to Fine Coarse Grained
Fine Grained
Porosity
Highly Porous
Less Porous
Specific Gravity
2.5-2.9
2.7
Transparency
Opaque
Opaque
Density
2.8-2.9 g/cm3
2.43-2.45 g/cm3
Resistance
Impact Resistant, Pressure Resistant, Water Resistant
Heat Resistant, Impact Resistant, Wear Resistant
Deposits in Eastern Continents
Asia
Afghanistan, Bangladesh, Bhutan, China, India, Japan, Kazakhstan, Malaysia, Pakistan, Russia, Thailand, Turkey, Vietnam
China, India, Iran, Saudi Arabia, Sri Lanka, Taiwan, Thailand, Turkey, Vietnam
Africa
Egypt, Ethiopia, Morocco, Nigeria, South Africa
Angola, Egypt, Madagascar, Namibia, Nigeria, South Africa
Europe
Austria, England, France, Georgia, Germany, Italy, Liechtenstein, Monaco, Norway, Slovenia, Spain, Sweden, Switzerland
Bulgaria, England, Germany, Norway, Romania, Switzerland
Deposits in Western Continents
North America
Canada, Costa Rica, Cuba, Mexico, Panama, USA
USA
South America
Brazil, Colombia, Guyana
Brazil, Chile
Deposits in Oceania Continent
Australia
New South Wales, New Zealand, Queensland
New Zealand, Queensland, South Australia, Western Australia