Crystals are the most lucid testimony to the strict order that
exists in the domain of rocks and minerals. The form of a crystal, that is the arrangement of its faces and angles, is rigorously
based on the form and arrangement of the atoms forming that
crystal. With that, crystallization handsomely illustrates the theorem of fractalism, referred to in the prologue.
Many of the minerals and rocks on earth are crystalline.
Crystals are omnipresent, although they do not always manifest
themselves by regular, geometric forms and lustrous facets. One
might say that, for the lithosphere, crystallization is as essential
as cell growth is for the biosphere. Perhaps the two are not as
far apart as we often intimate, prejudiced as we are in our strict
separation of the organic and the inorganic, of life and death.
DO US This group of scalenohedric calcite crystals, illuminated from underneath, might be a mock-up of one of these prestigious, all-glass buildings, at night in a deserted city. Actual width
140mm.
QUA T2 Quartz is the mineral silica (SiO,) in its crystalline
form. Quartz is, after feldspar, the most common rock-forming
mineral of the Earth's crust. Quartz is also synonymous with
brilliance and glitter, if not with magical power. Quartz is the
ultimate embodiment of crystallinity. Nearly all minerals, and
many synthetic materials, occur as crystals or form crystals, but
none on the scale and with such variety of forms as quartz.
Actual size 50 mm.
A DESITE Twinned crystals of feldspar float in a finely crystalline matrix, like lost spaceships. Andesite is a volcanic rock in
which such a divergence between large crystals (phenocrysts)
and a finely crystalline matrix is typical. This texture is called
porphyritic and it results from 'exsolution', a process of separation that takes place during successive phases of crystallization
in the lava. This picture is of a thin section exposure (for explanation see page 112). Actual size 20 x 26 mm.
FAYALI E Fayalite is the iron rich member of the olivine minerai suite, forsterite being the magnesium rich member at the
other end of this suite of iron-magnesium silicates. Most natural
olivines are a mixture of the two. This specimen however is
nearly pure fayalite, in an rare pattern of tabular crystals, covered with symmetrical striations (see page 113) Actual size 50
x 65 mm.
CRYSTAL
44
Crystals grow by the layer-upon-Iayer precipitation of sheets of atoms, from a surrounding smelt or solution,
on crystal planes already formed.The growth of a crystal may be
arrested, for longer or shorter periods, because the supply of
new molecules from the surrounding source is interrupted by
changed circumstances. Full-grown crystals often exhibit traces
of intermediate crystal planes resulting from such interruptions.
These are appropriately called ghost structures or phantoms, as
seen here in a group of amethyst crystals. This exposure is of a
thin section (for explanation see page 112), with an actual size
no larger than 15 x 25 mm.
EBULLITION Facetted crystalline spheres of pyrite like
these, up to the size of a golf ball, are found in black slates in the
area around Millstream, West Australia. Retrieving these fascinating nodules is only for the real 'rock hounds'. The slates are
hard to come by, as they occur underwater, in creeks and caves.
The slabs retrieved then have to be cleaved in a special way
before one knows whether they contain any such nodules or
not.
IDMANNSTETTERSCHE FIGUREN Widmannstetter
structures are a distinctive pattern of intertwined crystals in
iron-nickel meteorites, made visible by chemical etching of a
polished surface of such meteorites. They are named after the
first man to study them, Aloys von Widmannstetter, scientist and
director of the Technical Museum of Vienna in the early 19th
Century.The structures seen in this plate are in a piece from the
Gibeon, a well-known, large meteorite that fell in the Namibian
desert in prehistoric times. Because this meteorite hit the
earth's surface at a relatively flat angle, it rebounded in many
small pieces that were strewn around over a large area. Since
these chunks did not penetrate deeply into the soil and were
well preserved, many pieces were and still are retrieved by man.
Ancient African tribes used metal of the Gibeon for weaponry
and other utensils. For them this metal was godsend, since it
would not rust, which, as we now know, is thanks to the nickel
content. Actual size 95 x 120 mm.
PYRITE Pyrite is iron-sulphide, a common and widespread
iron-mineral. It belongs in the cubic crystal system, and welldeveloped crystals of pyrite can be perfect cubes (hexaeders)
with smooth metallic surfaces. Romantics and dreamers are
known to mistake glossy grains in freshly broken rock for gold
exists in the domain of rocks and minerals. The form of a crystal, that is the arrangement of its faces and angles, is rigorously
based on the form and arrangement of the atoms forming that
crystal. With that, crystallization handsomely illustrates the theorem of fractalism, referred to in the prologue.
Many of the minerals and rocks on earth are crystalline.
Crystals are omnipresent, although they do not always manifest
themselves by regular, geometric forms and lustrous facets. One
might say that, for the lithosphere, crystallization is as essential
as cell growth is for the biosphere. Perhaps the two are not as
far apart as we often intimate, prejudiced as we are in our strict
separation of the organic and the inorganic, of life and death.
DO US This group of scalenohedric calcite crystals, illuminated from underneath, might be a mock-up of one of these prestigious, all-glass buildings, at night in a deserted city. Actual width
140mm.
QUA T2 Quartz is the mineral silica (SiO,) in its crystalline
form. Quartz is, after feldspar, the most common rock-forming
mineral of the Earth's crust. Quartz is also synonymous with
brilliance and glitter, if not with magical power. Quartz is the
ultimate embodiment of crystallinity. Nearly all minerals, and
many synthetic materials, occur as crystals or form crystals, but
none on the scale and with such variety of forms as quartz.
Actual size 50 mm.
A DESITE Twinned crystals of feldspar float in a finely crystalline matrix, like lost spaceships. Andesite is a volcanic rock in
which such a divergence between large crystals (phenocrysts)
and a finely crystalline matrix is typical. This texture is called
porphyritic and it results from 'exsolution', a process of separation that takes place during successive phases of crystallization
in the lava. This picture is of a thin section exposure (for explanation see page 112). Actual size 20 x 26 mm.
FAYALI E Fayalite is the iron rich member of the olivine minerai suite, forsterite being the magnesium rich member at the
other end of this suite of iron-magnesium silicates. Most natural
olivines are a mixture of the two. This specimen however is
nearly pure fayalite, in an rare pattern of tabular crystals, covered with symmetrical striations (see page 113) Actual size 50
x 65 mm.
CRYSTAL
44
Crystals grow by the layer-upon-Iayer precipitation of sheets of atoms, from a surrounding smelt or solution,
on crystal planes already formed.The growth of a crystal may be
arrested, for longer or shorter periods, because the supply of
new molecules from the surrounding source is interrupted by
changed circumstances. Full-grown crystals often exhibit traces
of intermediate crystal planes resulting from such interruptions.
These are appropriately called ghost structures or phantoms, as
seen here in a group of amethyst crystals. This exposure is of a
thin section (for explanation see page 112), with an actual size
no larger than 15 x 25 mm.
EBULLITION Facetted crystalline spheres of pyrite like
these, up to the size of a golf ball, are found in black slates in the
area around Millstream, West Australia. Retrieving these fascinating nodules is only for the real 'rock hounds'. The slates are
hard to come by, as they occur underwater, in creeks and caves.
The slabs retrieved then have to be cleaved in a special way
before one knows whether they contain any such nodules or
not.
IDMANNSTETTERSCHE FIGUREN Widmannstetter
structures are a distinctive pattern of intertwined crystals in
iron-nickel meteorites, made visible by chemical etching of a
polished surface of such meteorites. They are named after the
first man to study them, Aloys von Widmannstetter, scientist and
director of the Technical Museum of Vienna in the early 19th
Century.The structures seen in this plate are in a piece from the
Gibeon, a well-known, large meteorite that fell in the Namibian
desert in prehistoric times. Because this meteorite hit the
earth's surface at a relatively flat angle, it rebounded in many
small pieces that were strewn around over a large area. Since
these chunks did not penetrate deeply into the soil and were
well preserved, many pieces were and still are retrieved by man.
Ancient African tribes used metal of the Gibeon for weaponry
and other utensils. For them this metal was godsend, since it
would not rust, which, as we now know, is thanks to the nickel
content. Actual size 95 x 120 mm.
PYRITE Pyrite is iron-sulphide, a common and widespread
iron-mineral. It belongs in the cubic crystal system, and welldeveloped crystals of pyrite can be perfect cubes (hexaeders)
with smooth metallic surfaces. Romantics and dreamers are
known to mistake glossy grains in freshly broken rock for gold