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GeneralColoring agent for "Salmon Calcite"

13th Jul 2018 17:58 UTCKelly Nash 🌟 Expert

This 10-cm. chunk of orange calcite from the MacDonald Mine, near Hybla, Ontario, looks very much like the "salmon calcite" from Franklin, New Jersey, and other locations. Does anyone know what the typical coloring agent or cause for this color is?

13th Jul 2018 19:53 UTCJeff Weissman Expert

From Franklin, its manganese - typically weathered examples have a black crust of manganese oxides

13th Jul 2018 21:05 UTCRichard Gunter Expert

Hi Kelly:

Orange "Salmon" calcite is fairly common in the veins and pegmatites of the southern Grenville Province in Ontario and Quebec. As far as I know it is iron impurities, often along grain boundaries. There have been a number of studies of these "vein-dykes" and pegmatites so there is a lot of data.

13th Jul 2018 21:41 UTCBob Harman

More than 90% of orange calcite is more correctly called iron stained or rusty colored calcite as most of this stuff is just staining with iron oxides. One helpful hint is the variations in color shades through out the specimen; the coloring is not quite uniform. CHEERS.......BOB

13th Jul 2018 21:45 UTCKelly Nash 🌟 Expert

Thanks to you both. Although the color is very similar, as I recall, manganese is believed to be the activator for the bright fluorescence of Franklin calcite, but this stuff from the MacDonald pegmatite (which was abundant at one time) is not fluorescent at all.

13th Jul 2018 22:45 UTCThomas Lühr Expert

Too much manganese quenches

13th Jul 2018 23:14 UTCRichard Gunter Expert

Very little of the Ontario and Quebec "Salmon Calcite" is fluorescent and none on the scale of the Franklin calcite. Manganese is not a common element in the Grenville so it is probably not an impurity in this calcite.

13th Jul 2018 23:22 UTCKelly Nash 🌟 Expert

Thanks, Thomas. Trying to ferret this out online is tough, since most of the "research" that comes up on google is on the "healing properties". But, I did find a good paper online just now, from the Canadian Mineralogist (Shaw et al, 1963, THE PETROLOGY AND GEOCHEMISTRY OF SOME GRENVILLE SKARNS), which says "The salmon-pink colour is probably caused by the presence of Mn and Fe", and "although the color varies in the rocks" (from pink to white), "Since the same colours occur in diamond drill core, it is not likely that they are of surficial origin" (so, not rust stains).

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