CaCO₃           Zn₂SiO₄

Daylight view

Calcite and willemite, fluorescing reddish-orange and green, respectively, under short-wave UV. Franklin, NJ. Width 14 cm.

Calcite fluoresces bright reddish-orange under short-wave ultraviolet light, and willemite fluoresces bright yellow-green under short-wave ultraviolet light. The response by both is generally weaker under long-wave ultraviolet light.

Minor amounts of manganese are responsible for both the reddish-orange fluorescence of calcite and the green fluorescence of willemite. For a discussion, see Warren et al. (1996).

Calcite and willemite, fluorescing reddish-orange and green, respectively, under short-wave UV. Franklin, NJ. Width 9 cm.

Daylight view

Calcite and willemite, detail from specimen above. Franklin, NJ. Width 2 cm.

Calcite is the predominant mineral of the entire Franklin Marble rock unit, extending many miles in outcrop. However, it is only that calcite that is within a meter or so of the two Zn-Mn-Fe orebodies at Franklin and Sterling which contains the required manganese and fluoresces.

Calcite and willemite, fluorescing reddish-orange and green, respectively, under short-wave UV. Secondary willemite filling fractures in calcite matrix. Sterling Hill, NJ. Width 12 cm.

Willemite was a major ore of zinc, and was recovered in millions of tons from the two orebodies. Some samples are also brightly phosphorescent pale green.

Some calcite and willemite samples give anomalous fluorescent responses. See Bostwick (1992) or the entry in the fluorescent list of this Website.

Be sure to visit the photo page taken under shortwave ultraviolet light.