Matrix coated by translucent colorless opal
Origin: Mexico
Sample size: 8 x 11 x 5 cm (top), 4 x 5 x 2 cm (bottom)

Origin: Spruce Pine, North Carolina, U.S.A.
Transparent colorless bubbly botryoidal hyalite opal covering a 3 x 3.5 cm
area on a
chalcedony matrix.
Origin: Cerra de la Rosa de Castilla, Guanajuato, Mexico
Dealer in
fine mineral specimens
Origin: Rodriguez Dam, near Tijuana, Baja California Norte, Mexico
Sample size: 7.4 x 4.5 x 2.1 cm
Origin: Rodriguez Dam, near Tijuana, Baja California Norte, Mexico
Sample size: 3.9 x 3.4 x 2.4 cm
Opalized clams and gastropod
Origin: Coober Pedy, South Australia, Australia
Sample size: 7.4 x 7.3 x 3.6 cm
Globular or botryoidal aggregates of white to greenish yellow opal variety
fiorite; the larger sample shows the coarse grained granitic hostrock
Origin: Castro Daire, Northern Portugal
Sample size: 6 x 10 cm (top), 3 x 3 cm (bottom)
Colourless to grey globular concretions on matrix
Origin: Nieder-Ofleiden, Homberg (Ohm), Hessen, Germany
Sample size: 5.5 x 7 cm