What does the word aphanitic mean?
Aphanitic is a descriptive term for small crystals and phaneritic for larger ones. … aid of a microscope (called aphanitic from the Greek aphanēs meaning “invisible”) or contains no minerals at all (in the latter case the rock is composed of glass which is a highly viscous liquid).
What does Aphanitic texture mean?
What does the term porphyritic mean?
Definition of porphyritic
1 : of or relating to porphyry. 2 : having distinct crystals (as of feldspar) in a relatively fine-grained base.
What does felsic stand for?
Felsic refers to silicate minerals magma and rocks which are enriched in the lighter elements such as silicon oxygen aluminium sodium and potassium. Felsic magma or lava is higher in viscosity than mafic magma/lava. Felsic rocks are usually light in color and have specific gravities less than 3.
How do you pronounce Aphanitic?
Is quartz an Aphanitic?
Aphanites are commonly porphyritic having large crystals embedded in the fine groundmass or matrix. … They consist essentially of very small crystals of minerals such as plagioclase feldspar with hornblende or augite and may contain also biotite quartz and orthoclase.
What does Aphanitic texture look like?
What is an aphanitic igneous rock?
What is the opposite of aphanitic?
Aphanitic (a = not phaner = visible) rocks in contrast to phaneritic rocks typically form from lava which crystallize rapidly on or near Earth’s surface. When extrusive rocks make contact with the atmosphere they cool quickly so the minerals do not have time to form large crystals.
Does obsidian exist?
What rock is glassy?
How fast do porphyritic rocks cool?
Porphyritic:a mixture of large and small crystals – perhaps a two-stage cooling history with the large crystals (the phenocrysts) cooling slowly and the small crystals (the groundmass) cooling more quickly.
What is felsic lava?
Felsic lavas are low temperature lavas because lower temperatures are required to keep felsic minerals molten (and if it was hotter it would have incorporated more iron and magnesium in comparison to silica). … So mafic lavas are hot low in silica and volatiles and have relatively low viscosity.
What is another word for felsic?
Rocks with greater than 90% felsic minerals can also be called “leucocratic” meaning ‘light-coloured’.
What is felsic and mafic?
In a widely accepted silica-content classification scheme rocks with more than 65 percent silica are called felsic those with between 55 and 65 percent silica are intermediate those with between 45 and 55 percent silica are mafic and those with less than 45 percent are ultramafic.
How can we say that a rock is Aphanitic?
Of or relating to an igneous rock in which the crystals are so fine that individual minerals cannot be distinguished with the naked eye. Aphanitic rocks are extrusive rocks that cooled so quickly that crystal growth was inhibited.
What is the difference between Aphanitic and Phaneritic textures?
APHANITIC TEXTURE – Igneous rocks that form on the earth’s surface have very fine-grained texture because the crystals are too small to see without magnification. PHANERITIC TEXTURE – Igneous rocks with large visible crystals because the rock formed slowly in an underground magma chamber.
How do you say pegmatites?
What is the composition of Aphanitic?
Aphanitic extrusive igneous rocks therefore have coarse-grained intrusive counterparts with the same chemical and mineral composition. … Both rock types are composed mainly of the silicate minerals quartz and orthoclase feldspar but the crystals in the rhyolite are too small to see without a microscope.
Is there olivine in granite?
What rock is intrusive?
intrusive rock also called plutonic rock igneous rock formed from magma forced into older rocks at depths within the Earth’s crust which then slowly solidifies below the Earth’s surface though it may later be exposed by erosion. Igneous intrusions form a variety of rock types.
How do pyroclastic rocks form?
Pyroclastic rocks are rocks formed by accumulation of material generated by explosive fragmentation of magma and / or previously solid rock during the course of a volcanic eruption.
Where are pegmatite rocks found?
What is a Phenocrysts in geology?
A relatively large crystal embedded in a finer-grained or glassy igneous rock. The presence of phenocrysts gives the rock a porphyritic texture (see illustration). Phenocrysts are represented most commonly by feldspar quartz biotite hornblende pyroxene and olivine.
Which samples contain fossils?
Mudstone shale and limestone are examples of sedimentary rock likely to contain fossils. As the layers of sediment build up on top of one another they create a physical timeline. The oldest layers along with the organisms that were fossilized as they formed are deepest. The youngest layers are found at the top.
What is pegmatite texture?
What type of rock is obsidian?
What are the 4 different textures of igneous rocks?
- COARSE GRAINED TEXTURE (PHANERITIC) mineral grains easily visible (grains several mm in size or larger)
- B) FINE GRAINED TEXTURE (APHANITIC) mineral grains smaller than 1mm (need hand lens or microscope to see minerals)
- C) PORPHYRITIC TEXTURE (MIXED FINE AND COARSE)
Where do you find peridotite?
Why is obsidian so dark?
Obsidian is commonly a translucent dark brown or black. Unlike basalt obsidian’s dark color is due to high amounts of impurities rather than the presence of dark colored minerals. The color of obsidian depends on the chemical composition of the impurities.
Is purple obsidian real?
Is obsidian sharper than diamond?
Surprisingly the edge of a piece of obsidian is superior to that of a surgeon’s steel scalpel. It is 3 times sharper than diamond and between 500-1000 times sharper than a razor or a surgeon’s steel blade resulting in easier incisions and fewer microscopic ragged tissue cuts.
Can lava turn into glass?
Which is the only rock that can float on water?
What does aphanitic mean?
What is the meaning of the word APHANITIC?
Igneous Rock Textures