Crystal system: Orthorhombic
Density: 3.18 gms/cm3
Colour: Yellow-orange to brown.
Norbergite occurs in the Franklin marble as small grains that fluoresce a pale yellow colour in ultraviolet radiation. Also occurring as small grains in the marble is the mineral diopside, formula CaMgSi2O6. Diopside fluoresces blue
When both norbergite and diopside occur together in Franklin calcite some very attractive fluorescent mineral specimens are obtained.
The picture shows a colourful specimen of Norbergite (fluorescing pale yellow) and Diopside (fluorescing blue) in short wave ultraviolet radiation. The specimen is from Ogdensberg, New Jersey.