Tennessee

Calcite
Well defined golden-yellow single X, 3.3 cm high, on dolostone matrix
11x10cm
Elmwood mine, Tennessee. Usa
Specimen n.436

Calcite
Prismatic XX of yellowish calcite, up to 3.1 cm long
8x4cm
Elmwood mine, Tennessee. Usa
Specimen n.1444

Fluorite
Pale purple cubic XX, edge up to 3.6cm, on black sphalerite
10x7.5cm
Elmwood mine, Tennessee. USA
Specimen n.581

Fluorite
Pale purple cubic XX, edge up to 2cm, on ruby dark sphalerite, a classic piece
5.5x5cm
Elmwood mine, Tennessee. USA
Specimen n.675

Illinois

Fluorite
Cubic XX, max edge 3.5cm, on a complex of calcite growing XX, terminated. The fluorite X in evidence has a 2.8cm edge and is very well defined. This is a specimen from the fluorspar mine which was closed in 1996
20x9cm
Minerva mine n.1, Cave-in-Rock District, llinois. USA
Specimen n.432

Fluorite
Cubic intergrown XX, max edge 5.1cm. The combination of yellow and dark purple is very fine
9x8cm
minerva mine n.1, Cave-in-Rock District, Illinois. USA
Specimen n.429

Fluorite
Transparent cubic X, 2 cm edge, matrix based. The X  shows a  clear phantom inside, the external part of the crystal is purple tinged.
8x6cm
Annabel Lee mine, Illinois. USA
Specimen n.353

Indiana

Calcite
Yellow semitransparent XX, up to 7.7 cm long, with some betumen on limestone
10x12cm
Meshberger stone co. quarry, Columbus, Indiana. USA
Specimen n.1309

Missouri

Calcite
XX up to 3xm, some double terminated, on matrix covered by dolomite and chalcopyrite in small XX
8x8cm
Sweetwater mine, Viburnum Trend District, Missouri. USA
Specimen n.639

Galena
Single cube, edge max is 5.8. A typical sample from Viburnum 
10x8.5cm
Miliken mine, Viburnum Trend District, Missouri. USA
Specimen n.321

Sphalerite
Large XX of black sphalerite, on a matrix covered by a lot of small red semistransparent sphalerite XX
12x12cm
Joplin Field, Jasper Co., Missouri. USA
Specimen n.327

Another photo: entire piece

Arizona

Fluorite
Group of octahedral XX, edge up to 0.9 cm. The XX, white opaque, are covered by a coating of oxides, I suppose copper oxides
9x5.5cm
Monarch mine, Yavapai Co., Arizona. USA
Specimen n.444

Glauberite
Characteristic steep bipyramidal floating crystal, slightly striated, of this uncommon mineral (maybe it is a pseudomorphosis of calcite after glauberite; more common to find empty cast or pseudomorphs in localities where little or no glauberite currently exists. It forms in evaporite and clay deposits and it is soluble in water). Twinned with a little crystal. From the most famous occurrence
6x3cm
Camp Verde, Yavapai Co., Arizona. USA
Specimen n.220

Wulfenite
Well defined tabular X, elongated, 1.2cm tall, on matrix. Color is brownish-red and X is very bright
7x6cm
Red Cloud mine, La Paz Country, Arizona. USA
Specimen n.775

Another photo: entire piece

Wulfenite
Parallel XX 2.8x1.2cm wide, bright and semitransparent, on matrix. The crystallized area of the photo is 1.2x1.5cm (one side of the specimen, with XX on both sides). This mine is famous for these red wulfenite XX
2.7x5cm
Red Cloud mine, La Paz Country, Arizona. USA
Specimen n.389

California

Andradite var melanite
Some bright and well formed XX, edge up to 0.7cm
9x8cm
San Benito Co, California. USA
Specimen n.405

New Mexico

Smithsonite
Green grains and botryoidal masses, on mineralized matrix 
7.5x6cm
Kelly mine, Magdalena District, New Mexico. USA
Specimen n.659

Smithsonite
Lilac-purple botryoidal mass
8x7cm
Kelly mine, Magdalena District, New Mexico. USA
Specimen n.658