40]Ar datings on the Ocotal stock yield 78-80 Ma ages for well-preserved fayalite
gabbros, one dolerite and separated fresh plagioclase from a ferrohortonolite-bearing gabbro.
Only a small amount of fayalite
was available, so the crystals were crushed to powder between glass slides.
then solidifies around the grains, gluing the sand onto the surface of the casting.
Associated minerals are: zircon, quartz, kainosite-(Y), aegirine, [beta]-fergusonite-(Y), yttrian ilvaite, ilvaite, hingganite-(Ce), neodymian allanite-(Ce), magnetite, fayalite
The role of iron oxide in preventing porosity has long been linked with its ability to react with silica to form fayalite
, which forms a "physical" barrier, preventing gas solution.
The following standards were used: diopside (Si, Ca), spessartine (Mn), fayalite
(Fe), andalusite (Al) and forsterite (Mg).
Most foundrymen were taught that seacoal acts by burning and producing a reducing atmosphere, which prevents oxidation of the cast iron, and consequently prevents the formation of fayalite
and ultimately Penetration.
Standards used were pure niobium and tantalum metals (Nb, Ta), Rockport fayalite
(Fe), Nuevo garnet (Mn) and Webster fosterite (Mg).
When comparing the Gibbs Free Energy of Formation for mullite, fayalite
and tephroite, the reactions between the iron- and manganese oxides and the silica will have the following values:
Associated minerals are: fayalite
, magnetite, quartz, annite, laihunite, and clinoamphiboles (only at the Colorado locality).
This leads to high levels of FeO in the bath, forming fayalite
and other low-melting point slags that carry over into characteristic "bird shot" defects.
Associated minerals are: quartz, magnetite, spessartine-rich garnet, "apatite," sillimanite, ferroan gahnite, sulfides, Mn-rich grunerite (in places manganogrunerite), manganoan fayalite
and Mn-rich pyroxferroite.