IRON EARTHS

Miscellaneous

Family: None
Region: None
Mined At: Unspecified
Raw Mineral: Yes
Generic: No

Notes

(Richard Willis)

Iron is the third most abundant element in earths — first, aluminum (Al); second, silicon (Si). Just as “clay” contains Al and Si virtually by definition, virtually any clay contains iron (Fe) by fiat. see spinel
Ferric oxide earths, such as the “ochres”, with significant percentages of manganese and other metals make them suitable as engobes to smoke-scorch before glazing in order to blacken the clay body and to effect a metallic sheen. Primitive pottery was so colored and often then burnished, frequently with a graphite to increase the polished sheen. With the advent of glazes the iron-colored body was usually covered with a transparent glaze to effect the polish. Examples are the celadons of Chi na, the red-glost pottery of Rome, and the aka or “red” (black body, red glaze), raku wares of Korea and Japan. see Crocus Martis, limonite, ochre, etc.
popular iron-rich earths used in ceramics:
— yellow ochre: hydrated ferric oxide (Fe₂O₃) [see, also, the titled entry yellow ochre]
— red ochre: anhydrated ferric oxide
— black, or “shadow”, ochre: hydrated FeO plus Mn
typical analyses of popular iron-rich minerals
goethite — SiO₂ 5.4, Al₂O₃ 4.3, Fe₂O₃40.5, FeO 8.7, MnO 0.4, MgO 1.6, CaO 15.1, H₂O 7.2, TiO₂ 0.2, P₂O₃ 1.7, CO₂ 15.0, S 0.04
hematite — SiO₂ 9.9, Al₂O₃ 3.2, Fe₂O₃67.8, FeO 10.0, MgO 0.4, CaO 2.4, H₂O 2.8, TiO₂ 0.4, P₂O₃2.3, CO₂ 1.1
chamosite — SiO₂ 13.4, Al₂O₃ 7.4, Fe₂O₃ 8.5, FeO 31.9, MgO 2.5, CaO 6.1, H₂O 8.5, P₂O₃2.8, CO₂ 17.4, S 0.5
siderite— SiO₂ 7.8, Al₂O₃ 8.4, Fe₂O₃1.7, FeO 35.6, MnO 0.4, MgO 4.0, CaO 10.5, H₂O 4.2, TiO₂ 0.2, P₂O₃ 1.3, CO₂ 25.3, S 0.1

Authors

Richard Willis (Owner)

XML

<?xml version="1.0" encoding="UTF-8"?>
<material name="IRON EARTHS" descrip="" generic="0" rawmineral="1" searchkey="" loi="0.00">
<notes>
<note>Iron is the third most abundant element in earths &#151; first, aluminum (Al); second, silicon (Si). Just as &#147;clay&#148; contains Al and Si virtually by definition, virtually any clay contains iron (Fe) by fiat. see spinel 
Ferric oxide earths, such as the &#147;ochres&#148;, with significant percentages of manganese and other metals make them suitable as engobes to smoke-scorch before glazing in order to blacken the clay body and to effect a metallic sheen. Primitive pottery was so colored and often then burnished, frequently with a graphite to increase the polished sheen. With the advent of glazes the iron-colored body was usually covered with a transparent glaze to effect the polish. Examples are the celadons of Chi
na, the red-glost pottery of Rome, and the aka or &#147;red&#148; (black body, red glaze), raku wares of Korea and Japan. see Crocus Martis, limonite, ochre, etc. 
popular iron-rich earths used in ceramics: 
&#151; yellow ochre: hydrated ferric oxide (Fe2O3) [see, also, the titled entry yellow ochre] 
&#151; red ochre: anhydrated ferric oxide 
&#151; black, or &#147;shadow&#148;, ochre: hydrated FeO plus Mn 
typical analyses of popular iron-rich minerals 
goethite &#151; SiO2 5.4, Al2O3 4.3, Fe2O3 40.5, FeO 8.7, MnO 0.4, MgO 1.6, CaO 15.1, H2O 7.2, TiO2 0.2, P2O3 1.7, CO2 15.0, S 0.04 
hematite &#151; SiO2 9.9, Al2O3 3.2, Fe2O3 67.8, FeO 10.0, MgO 0.4, CaO 2.4, H2O 2.8, TiO2 0.4, P2O3 2.3, CO2 1.1 
chamosite &#151; SiO2 13.4, Al2O3 7.4, Fe2O3 8.5, FeO 31.9, MgO 2.5, CaO 6.1, H2O 8.5, P2O3 2.8, CO2 17.4, S 0.5 
siderite&#151; SiO2 7.8, Al2O3 8.4, Fe2O3 1.7, FeO 35.6, MnO 0.4, MgO 4.0, CaO 10.5, H2O 4.2, TiO2 0.2, P2O3 1.3, CO2 25.3, S 0.1 

</note>
</notes>
</material>

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IRON EARTHS

Miscellaneous

Notes

(Richard Willis)

Authors

XML