Fluorite (blue), calcite (red).  Dal’negorsk, Siberia, Russia.  6” x 7” (15 x 18 cm). Translucent, sea-green, cubic fluorite crystals 1.0-2.5 cm on edge, upon a bed of white calcite crystals of similar dimension.  The blue fluorescence of the fluorite is activated by europium, and the red of the calcite by manganese.  LW.

Calcite. Crystal River #2 quarry, Lecanto, Citrus County, Florida. 7" x 6" (18 x 15 cm). Large group of pale amber "dogtooth" crystals 2-4 cm long. The fluorescence (and the daylight color) are probably due to organic impurities. LW.

Septarian nodule.  Near Orderville, Kane County, Utah.  6” x 6” (15 x 15 cm).   The yellow-fluorescing crystals lining the interior are calcite, and the darker, massive mineral lining cracks and rimming broken rock fragments reportedly is aragonite.  The smooth, gray exterior of these nodules hints nothing of their appearance when opened.  LW.

Calcite.  Irai, Rio Grande do Sul, Brazil.  6” x 3” (15 x 8 cm).  Large crystals of white calcite from a gas cavity in basalt.  The activator of fluorescence is probably manganese substituting for calcium.  SW.

Calcite (left). Lecanto, Citrus County, Florida. 5 x 1.4 inches (13 x 3.5 cm). An elongate, rodlike group of pale yellow calcite crystals 0.4-1.0 cm long. A small, circular hole extends through the center of this specimen along its entire length; similar holes are present in numerous other specimens from this locality. LW.

Calcite (right). Brooksville, Hernando County, Florida. 2 x 1.4 inches (5 x 3.5 cm). A flowerlike group of translucent, very pale yellow crystals. LW.

Quartz (“youngite”).  Near Guernsey, Platte County, Wyoming.  7” x 9” (18 x 23 cm).  Knobby druse of pale gray, translucent quartz encrusting brecciated fragments of pinkish-brown jasper.  The likely activator of the green fluorescence in this and most other green-fluorescing quartz and chalcedony worldwide is uranium, present in trace to minor amounts.  SW.

Calcite.  Cave-in-Rock district, Hardin County, Illinois.  6” x 9” (15 x 23 cm).  Large group of ivory-colored, scalenohedral crystals 1.5-3.0 cm long on matrix.  The rich golden-yellow fluorescence of this crystal group is unusual; calcite fluorescing white to pastel shades of yellow is much more common.  LW.

Hydrozincite.  Goodsprings district, Clark County, Nevada.  8” x 6” (20 x 15 cm).  Hydrozincite is one of the relatively few nonuranium minerals that shows a similar color of fluorescence regardless of locality.  Vuggy crystal specimens such as this one are particularly prized, for most hydrozincite is either massive or occurs as thin seams along fracture surfaces.  The activator of fluorescence remains unknown.  SW.

Fluorite.  Clay Center, Ohio.  6” x 4” (15 x 10 cm).  Fine group of transparent, pale honey-colored, intergrown, cubic crystals of fluorite 0.5-1.5 cm on edge.  The zoned fluorescence is common among specimens from this locality.  LW. 

Aragonite.  Cianciana, Sicily, Italy.  7” x 7” (18 x 18 cm).  Large group of dusky green, pseudohexagonal crystals 2-4 cm long.  A fluorescent classic.  Fine crystal groups of Sicilian aragonite grace many mineral collections worldwide, but good examples are becoming increasingly difficult to find.  LW.

Scheelite.  Trumbull, Fairfield County, Connecticut.  12” x 5” (30 x 13 cm).  One of the finest of the hundreds of specimens recently recovered from an excavation for a new shopping center near Trumbull, not far from the original Long Hill locality.  SW. 

Colemanite.  Calico Mountains, San Bernadino County, California.  6” x 6” (15 x 15 cm).  Massive, nodular colemanite in mudstone matrix.  LW.

Fluorite.  Allenheads mine, Allenheads, Northumberland, UK.  13” x 9” (33 x 23 cm).  Large plate of purple cubic crystals 1.0-2.5 cm on edge, on altered limestone.  The deep blue-violet fluorescence is due to minor amounts of europium substituting for calcium in the fluorite structure.  LW.

Calcite (manganoan). Pachapaqui mine, Huanuco, Peru. 4 x 3 inches (11 x 8 cm). A lovely group of divergent, pale pink, opaque, crudely formed "dogtooth" crystals free of matrix. SW.

Aragonite.  Sicily, Italy.  6” x 6” (15 x 15 cm).  Platelike group of 1-2 cm, dusky green, pseudohexagonal crystals on limestone and sulfur matrix.  The prominent zoning of the crystals is especially evident under SW ultraviolet light, as seen here.  This same specimen under LW ultraviolet light fluoresces bright pink.

Sphalerite.  Horn Silver mine, Frisco, Beaver County, Utah.  18” x 10” (46 x 25 cm).  Large mass of a mineralized solution-collapse breccia derived from original carbonate rock.  All of the observed colors of fluorescence—chiefly golden yellow, but also bluish green, dull red, and white—are reportedly due to sphalerite.  LW.