Skarns are calc-silicate rocks formed during contact metamorphism and metasomatism between an intrusive body and carbonate-rich sedimentary rocks. The hot fluids expelled from the intrusive contain iron, silica, magnesium, aluminium and a variety of incompatible elements. These fluids dissolve carbonates and precipitate calc-silicates in their place. The most common minerals that comprise skarns are epidote, garnet, idocrase, pyroxenes, wollastonite, tremolite, and magnetite or hematite. Calcite and quartz are generally also present. Mineralized skarns may be enriched in one or more of the following; Au, Ag, Cu, Zn, Pb, Fe, Mo, Sn, W. Au and Cu skarns are some of the most common type, others contain polymetallic sulfides (+/-Ag) such as the Nuestra Senora Ag-Zn-Cu-Pb skarn in Mexico, or Sn and W as the Ok Tedi and Pine Creek mines in California.

PETROGRAPHIC REPORTS will include microscopic examination of thin sections with transmitted and reflected lights, detailed description of mineralogy and texture, classification of rocks where possible, visually estimated modal proportion of minerals, and description of primary and secondary minerals and their paragenetic sequence. In mineralized samples, the genesis of ore will be estimated. All reports include 2 or more photomicrographs of each thin section taken by a digital Leica cooled camera, a cd with file(s) and 2 hard copies of the report.

(x-axis of photos: 1.6mm)

• Adularia (grey) in calcite. XN. Adularia (grey) in calcite. XN.
• Silver-rich chalcopyrite rims white galena Silver-rich chalcopyrite rims white galena
• Galena (white) is replaced by chalcopyrite Galena (white) is replaced by chalcopyrite
• Sphalerite, chalcopyrite & galena Sphalerite, chalcopyrite & galena
• Zoned grossular replaces calcite. XN Zoned grossular replaces calcite. XN
• Intergrowth of chalcopyrite and galena Intergrowth of chalcopyrite and galena
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