Definition
Trondhjemite is a leucocratic (light-colored) intrusive igneous rock. It is a variety of tonalite in which the plagioclase is mostly in the form of oligoclase. Trondhjemites are sometimes known as plagiogranites.
Dacite is a volcanic igneous rock which is rintermediate in composition between andesite and rhyolite
Origin
Tonale, Italy
Romania and Moldova, Europe
Discoverer
Unknown
Unknown
Etymology
From Trondheim, Norway
From Dacia, a province of the Roman Empire which lay between the Danube River and Carpathian Mountains where the rock was first described
Class
Igneous Rocks
Igneous Rocks
Sub-Class
Durable Rock, Hard Rock
Durable Rock, Soft Rock
Other Categories
Coarse Grained Rock, Fine Grained Rock, Medium Grained Rock, Opaque Rock
Fine Grained Rock, Medium Grained Rock, Opaque Rock
Texture
Phaneritic
Aphanitic to Porphyritic
Color
Black, Brown, Light to Dark Grey, White
Bluish - Grey, Brown, Grey, Light to Dark Grey
Durability
Durable
Durable
Appearance
Banded and Foilated
Vesicular
Interior Uses
Decorative Aggregates, Entryways, Flooring, Homes, Interior Decoration
Decorative Aggregates, Entryways, Interior Decoration
Exterior Uses
As Building Stone, As Facing Stone, Paving Stone, Garden Decoration, Office Buildings
As Building Stone, Paving Stone, Garden Decoration
Other Architectural Uses
Curbing
Curbing
Construction Industry
As Dimension Stone, Cement Manufacture, Cobblestones, Construction Aggregate, for Road Aggregate
As Dimension Stone, Construction Aggregate, for Road Aggregate, Landscaping
Antiquity Uses
Artifacts, Monuments, Sculpture, Small Figurines
Artifacts
Commercial Uses
Cemetery Markers, Creating Artwork
Commemorative Tablets, Creating Artwork
Types
Intermediate intrusive rock
Footwall Dacite, Hanging wall Dacite, Tuff and Biotite Dacite
Features
Is one of the oldest rock, Typically speckled black and white.
Host Rock for Lead, Is one of the oldest rock
Archaeological Significance
Formation
When alkali feldspar is extracted from granite, it changes to granitoid and later, it becomes trondhjemite with quartz as major mineral.
Dacitic magma is formed by the subduction of young oceanic crust under a thick felsic continental plate. Further, the Oceanic crust is hydrothermally altered as quartz and sodium are added.
Mineral Content
Albite, Amphibole, Apatite, Biotite, Feldspar, Hornblade, Ilmenite, Magnetite, Manganese Oxides, Olivine, Plagioclase, Pyroxene, Quartz, Sulfides, Titanite, Zircon
Amphibole, Apatite, Biotite, Feldspar, Garnet, Hornblade, Magnetite, Plagioclase, Pyroxene, Quartz, Zircon
Compound Content
NaCl, CaO, MgO, Silicon Dioxide
Ca, Fe, Potassium Oxide, Mg, Potassium, Silicon Dioxide
Types of Metamorphism
Burial Metamorphism, Cataclastic Metamorphism, Contact Metamorphism, Impact Metamorphism, Regional Metamorphism
Burial Metamorphism, Cataclastic 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, Sea Erosion, Water Erosion, Wind Erosion
Chemical Erosion
Grain Size
Medium to Fine Coarse Grained
Medium to Fine Coarse Grained
Fracture
Conchoidal
Conchoidal
Streak
Bluish Black
White
Porosity
Very Less Porous
Less Porous
Luster
Subvitreous to Dull
Subvitreous to Dull
Specific Gravity
2.86-3
2.86-2.87
Transparency
Opaque
Translucent
Density
2.73 g/cm3
2.77-2.771 g/cm3
Resistance
Heat Resistant, Pressure Resistant, Wear Resistant
Heat Resistant, Impact Resistant, Pressure Resistant, Wear Resistant
Deposits in Eastern Continents
Europe
Finland, Germany, Italy, Romania, Sweden, Turkey
France, Greece, Romania, Scotland, Spain
Deposits in Western Continents
South America
Argentina, Bolivia, Chile, Colombia, Ecuador, Peru
Argentina, Bolivia, Chile, Colombia, Ecuador, Peru, Venezuela
Deposits in Oceania Continent
Australia
New Zealand, South Australia, Western Australia
New Zealand, South Australia, Western Australia