continent officially declared opal to be their national gem. This
cut and polished Australian specimen is a Yowah Nut, a type in
which the opal is intercalated in the concentric fissures of a
limonite concretion. Actual size 30 x 50 mm.
Malachite, a copper carbonate with vivid green
colors and banded, kidney-like structures, is hard to mistake.
This polished slab comes from the Congolese copper-mining
province Shaba. Malachite, although closely associated with the
copper ore, is not an ore in its own right. Often malachite is
worked into trinkets and other small ornaments. More lavish
was its use to adorn the interior of tsarist palaces in Moscow
and St. Petersburg. This extravagance before long led to the
total depletion of the renowned malachite mines in Russia.
Actual size 90 x I 10 mm.
RU
ZOISITE Longida, in Tanzania, is a unique locality
for the occurrence of outsized, elongated crystals of ruby,
embedded in a green matrix of zoisite. This picture is of a thin
slice, craftily sawed off perpendicular to the long axis of the
crystal and polished on both sides. It is photographed with
transmitted light, so that all the intricacies of the ruby's crystal
structure can be well observed, including growth planes, cracks,
and fissures that resulted from stresses during crystal growth.
Actual diameter 100 mm.
U T L TI ES Milky blue chalcedony has here been
deposited in the form of small pinnacles and a sugary crust. As
explained for geodes and agates in the previous chapters, most
chalcedony is formed inside rock cavities, often in a rich variety
ofform and color. The pinnacles in this cavity are actually small
stalactites, formed by the drip-drip of water inside a small cavity, just like the formation of the much larger, calcitic stalactites
in caves. Actual size 60 x 80 mm.
THE FLYING DUTCH AN The ragged and ghostly ship of
the legendary Dutchman, who was condemned to an eternal
quest of the world's seas, may have appeared somewhat like
this to the bewildered seamen that ran across him, navigating
their ship across the waves, during faraway, stormy nights.
This scene occurs in a polished slab of Paesina Stone, see
explanation under Pietra Paesina. Actual size 100 x 130 mm.
LUCIFERThe mythological bearer of light materializes inside
97
a rhyolitic agate from West Australia. Rhyolite is a characteristic type of extrusive rock (see page 10) that is often the host
rock of Australian geodes. Actual size 35 x 45 mm.
cut and polished Australian specimen is a Yowah Nut, a type in
which the opal is intercalated in the concentric fissures of a
limonite concretion. Actual size 30 x 50 mm.
Malachite, a copper carbonate with vivid green
colors and banded, kidney-like structures, is hard to mistake.
This polished slab comes from the Congolese copper-mining
province Shaba. Malachite, although closely associated with the
copper ore, is not an ore in its own right. Often malachite is
worked into trinkets and other small ornaments. More lavish
was its use to adorn the interior of tsarist palaces in Moscow
and St. Petersburg. This extravagance before long led to the
total depletion of the renowned malachite mines in Russia.
Actual size 90 x I 10 mm.
RU
ZOISITE Longida, in Tanzania, is a unique locality
for the occurrence of outsized, elongated crystals of ruby,
embedded in a green matrix of zoisite. This picture is of a thin
slice, craftily sawed off perpendicular to the long axis of the
crystal and polished on both sides. It is photographed with
transmitted light, so that all the intricacies of the ruby's crystal
structure can be well observed, including growth planes, cracks,
and fissures that resulted from stresses during crystal growth.
Actual diameter 100 mm.
U T L TI ES Milky blue chalcedony has here been
deposited in the form of small pinnacles and a sugary crust. As
explained for geodes and agates in the previous chapters, most
chalcedony is formed inside rock cavities, often in a rich variety
ofform and color. The pinnacles in this cavity are actually small
stalactites, formed by the drip-drip of water inside a small cavity, just like the formation of the much larger, calcitic stalactites
in caves. Actual size 60 x 80 mm.
THE FLYING DUTCH AN The ragged and ghostly ship of
the legendary Dutchman, who was condemned to an eternal
quest of the world's seas, may have appeared somewhat like
this to the bewildered seamen that ran across him, navigating
their ship across the waves, during faraway, stormy nights.
This scene occurs in a polished slab of Paesina Stone, see
explanation under Pietra Paesina. Actual size 100 x 130 mm.
LUCIFERThe mythological bearer of light materializes inside
97
a rhyolitic agate from West Australia. Rhyolite is a characteristic type of extrusive rock (see page 10) that is often the host
rock of Australian geodes. Actual size 35 x 45 mm.