A lithophysa (plural lithophysae, from Greek lithos "stone" + physan "to blow")[1] is a felsicvolcanicrock with a spherulitic structure and interior cavity with concentric chambers. Its outer shape is spherical or lenticular. They vary in size from very small up to twelve feet in diameter depending on the age of the magma chamber. These rocks are usually found within obsidian or rhyolite lava flows.[2] Lavas low in feldspar minerals may produce a version known as snowflake obsidian.
A lithophysa from FranceA collection of lithophysae "thundereggs"
These cavities are believed to be caused by expanding gases in tuffs and rhyolitic lavas before solidification.[1] If the cavity becomes lined with crystals it may be referred to as a geode or if filled partially or fully with agate, jasper or opal it is called a thunderegg. The term vug is also used for similar cavities although the meaning of vug is usually restricted to cavities in rocks formed by the removal of material such as soluble minerals. These cavities usually contain layers of various colors (red, pink, gray, etc.) composed by crystals of quartz,[1]chalcedony,[3]hematite, fluorite[4] and various colored oxides or other minerals.[1]
Lithophysae from Richardson Ranch near Madras Oregon. 1, 2. Displaying typical plates and "sutures". 3, 4. A cluster with three spheroid centers. 5, 6. Example of slow fill structure layers with a large opal layer at the bottom. Expansion is controlled by where the water was located in the structure. 7. "Dimple" and "pimple" where expansion began on an inner shell. 8. Fortification agate
Lithophysae are one of the many forms of silica (SiO2),[3] as quartz,[1] agate,[1] opal,[1] chalcedony, etc. They can have an average diameter 5–20 centimetres (2.0–7.9 in),[3] but can be much larger (for example, 300–370 centimetres (10–12 ft) at Silver Cliff in Colorado). Lithophysae are also related to the spherulites found in obsidians on the Italian island of Lipari, in Yellowstone National Park, and other places.[5]
Spheroids form in high silica magmas
Spheroid "trains" in obsidian
Snowflake obsidian
A partially "blown" spheroid pair in obsidian
"Trains" of "blown" spheroids transformed to lithophysae
lithophysa, lithophysa, plural, lithophysae, from, greek, lithos, stone, physan, blow, felsic, volcanic, rock, with, spherulitic, structure, interior, cavity, with, concentric, chambers, outer, shape, spherical, lenticular, they, vary, size, from, very, small,. A lithophysa plural lithophysae from Greek lithos stone physan to blow 1 is a felsic volcanic rock with a spherulitic structure and interior cavity with concentric chambers Its outer shape is spherical or lenticular They vary in size from very small up to twelve feet in diameter depending on the age of the magma chamber These rocks are usually found within obsidian or rhyolite lava flows 2 Lavas low in feldspar minerals may produce a version known as snowflake obsidian A lithophysa from FranceA collection of lithophysae thundereggs These cavities are believed to be caused by expanding gases in tuffs and rhyolitic lavas before solidification 1 If the cavity becomes lined with crystals it may be referred to as a geode or if filled partially or fully with agate jasper or opal it is called a thunderegg The term vug is also used for similar cavities although the meaning of vug is usually restricted to cavities in rocks formed by the removal of material such as soluble minerals These cavities usually contain layers of various colors red pink gray etc composed by crystals of quartz 1 chalcedony 3 hematite fluorite 4 and various colored oxides or other minerals 1 Lithophysae from Richardson Ranch near Madras Oregon 1 2 Displaying typical plates and sutures 3 4 A cluster with three spheroid centers 5 6 Example of slow fill structure layers with a large opal layer at the bottom Expansion is controlled by where the water was located in the structure 7 Dimple and pimple where expansion began on an inner shell 8 Fortification agateLithophysae are one of the many forms of silica SiO2 3 as quartz 1 agate 1 opal 1 chalcedony etc They can have an average diameter 5 20 centimetres 2 0 7 9 in 3 but can be much larger for example 300 370 centimetres 10 12 ft at Silver Cliff in Colorado Lithophysae are also related to the spherulites found in obsidians on the Italian island of Lipari in Yellowstone National Park and other places 5 Spheroids form in high silica magmas Spheroid trains in obsidian Snowflake obsidian A partially blown spheroid pair in obsidian Trains of blown spheroids transformed to lithophysae Blown spheroid transformed to a lithophysa Blown spheroid transformed to a lithophysa Blown spheroids transformed to lithophysaeSee also editLava balloonReferences edit nbsp Wikimedia Commons has media related to Lithophysa a b c d e f g What Are Lithophysae Roger Weller Lithophysae cluster a b c Geowiki Mineralienatlas Geological Survey Bulletin Ed 136 nbsp This article about igneous petrology is a stub You can help Wikipedia by expanding it vte Retrieved from https en wikipedia org w index php title Lithophysa amp oldid 1188459908, wikipedia, wiki, book, books, library,
