Veining can be reduced or avoided by the use of more refractory non-silica sands ( zircon, chromite etc ); by flux additives which lower the temperature of silica transition to tridymite or cristobalite, or which sinter the sand increasing resistance to failure; or by organic additives which are decomposed to carbon at high temperature, which then bonds to silica increasing strength, imparting veining resistance.
42.
"' Seifertite "'is a Martian where it is presumably formed from either tridymite or cristobalite other polymorphs of quartz as a result of heating during the atmospheric re-entry and impact to the Earth, at an estimated minimum pressure of 35 GPa . It can also be produced in the laboratory by compressing cristobalite in a diamond anvil cell to pressures above 40 GPa . The mineral is named after Friedrich Seifert ( born 1941 ), the founder of the Bayerisches Geoinstitut at University of Bayreuth, Germany, and is officially recognized by the International Mineralogical Association.
43.
"' Seifertite "'is a Martian where it is presumably formed from either tridymite or cristobalite other polymorphs of quartz as a result of heating during the atmospheric re-entry and impact to the Earth, at an estimated minimum pressure of 35 GPa . It can also be produced in the laboratory by compressing cristobalite in a diamond anvil cell to pressures above 40 GPa . The mineral is named after Friedrich Seifert ( born 1941 ), the founder of the Bayerisches Geoinstitut at University of Bayreuth, Germany, and is officially recognized by the International Mineralogical Association.
