What is the mineral composition of obsidian?
Obsidian consists mainly of SiO2 (silicon dioxide), usually 70% by weight or more. Crystalline rocks with a similar composition include granite and rhyolite.
What minerals are in syenite?
Syenite is a coarsely crystalline plutonic intermediate rock consisting chiefly of alkali feldspar with less than 5% quartz and/or feldspathoid. Clinopyroxene, hornblende, biotite mica, or olivine may be present in minor proportions.
What is the texture and composition of obsidian?
Obsidian
| Type | Igneous Rock |
|---|---|
| Texture | Glassy |
| Origin | Extrusive/Volcanic |
| Chemical Composition | Felsic |
| Color | Reddish Brown mottled with black |
Is syenite felsic or mafic?
Compilations of many rock analyses show that rhyolite and granite are felsic, with an average silica content of about 72 percent; syenite, diorite, and monzonite are intermediate, with an average silica content of 59 percent; gabbro and basalt are mafic, with an average silica content of 48 percent; and peridotite is …
How is autumn obsidian made?
Obsidian is formed by rapidly cooling felsic lava extruded from a volcano with limited growth in crystals. While obsidian is usually dark in colour, similar to basalt-like mafic rocks, the composition of obsidian is extremely felsic. Obsidian mainly consists of SiO2 (silicon dioxide), typically 70% or more.
Is obsidian a mixture?
Volcanic glass – a rock rather than a mineral, it is a mixture of cryptocrystalline grains of silica minerals in a glass-like suspension, a super-cooled liquid.
What is the syenite made of?
syenite, any of a class of intrusive igneous rocks essentially composed of an alkali feldspar and a ferromagnesian mineral. A special group of alkali syenites is characterized by the presence of a feldspathoid mineral such as nepheline, leucite, cancrinite, or sodalite (see nepheline syenite).
How is syenite formed?
Syenites are products of alkaline igneous activity, generally formed in thick continental crustal areas, or in Cordilleran subduction zones. To produce a syenite, it is necessary to melt a granitic or igneous protolith to a fairly low degree of partial melting.
Is obsidian conductive?
The mineral has no electrical conductivity, is not radioactive, and melts at a temperature of 1200 to 1500 degrees Celsius.
Does obsidian have air bubbles?
Obsidian is the result of volcanic lava coming in contact with water. Obsidian can contain small bubbles of air that are aligned along layers created as the molten rock was flowing just before being cooled.
What is the chemical formula for syenite?
Al2KNaO8Si2
Nepheline syenite | Al2KNaO8Si2 – PubChem.