and pyrite's nickname is therefore 'fool's gold'. Actual size 70 x
Il0mm.
The hexagonal crystals of aquamarine have a
neat, columnar arrangement in this group. Aquamarine is a variety of beryl and is often found in pegmatites, complex rock
suites formed at great depth, often the source of ores and semi
precious stones. The micaceous mineral surrounding the crystals is muscovite, also typical for pegmatite. The color of aquamarine varies from green to blue, like the waters of the sea,
hence its name. Actual size 50 x 65 mm.
REFLECTIO S FRO OUTE SPACE A set of parallel
crystal planes, in a group of rhombic calcite crystals, reflects the
light of a sparsely clouded, blue sky.Actual size 50 x 70 mm.
IMICRY What looks like butterfly wings or the feathers of an
exotic bird is actually a thin section exposure of prehnite.
Prehnite is an inconspicuous, soft-green mineral, forming radial
crystals inside voids in igneous and metamorphic rocks. In thin
section with transmitted polarized light, the radial crystals of
this mineral take on high order refractive colors. Actual size 18
x 22 mm.
TUR All EHarpoon-like, this large turmaline crystal punctures a matrix of chlorite, which is deposited in the form of
small, rosette-shaped aggregates. Thin section, transmitted
polarized light. Actual size 15 x 20 mm.
OLF
IT Wolframite is the principal ore for tungsten, a
metal used for the manufacture of lamp filaments and other
industrial products. The gleam of spectral colors results from a
wafer-thin veneer of chalcopyrite, which covers the tubular
crystals of the wolframite. Actual size 20 x 25 mm.
AUGITEThis is a thin section exposure, in polarized light, of a
cluster of augite crystals. Augite is a mineral from the pyroxene
group and the individual crystals typically show parallel bands of
internal zoning. Clusters of crystals like these grow out of a central nucleation point and they usually occur in potash rich lava's.
The actual size of this crystal is no more than 8 mm.
CALCIT GLOBULES Calcite is the crystalline variety of
calcium carbonate, a mineral that occurs in many forms. Shells,
4S
corals, limestone and marble are also calcium carbonate. The
globules seen here are formed by radial, crystalline growth in a
void inside lava and they are a rarity. Actual size 40 x 60 mm.
CALCITE 0
FLUORITE Like a stranded space vehicle,
this double-ended crystal of calcite has nested itself on an earlier formed group of fluorite crystals. Quartz was just characterized as the 'ultimate embodiment' of crystallinity, but calcite
comes a close second, as seen in other examples in this chapter.
Actual size 80 x 90 mm.
Il0mm.
The hexagonal crystals of aquamarine have a
neat, columnar arrangement in this group. Aquamarine is a variety of beryl and is often found in pegmatites, complex rock
suites formed at great depth, often the source of ores and semi
precious stones. The micaceous mineral surrounding the crystals is muscovite, also typical for pegmatite. The color of aquamarine varies from green to blue, like the waters of the sea,
hence its name. Actual size 50 x 65 mm.
REFLECTIO S FRO OUTE SPACE A set of parallel
crystal planes, in a group of rhombic calcite crystals, reflects the
light of a sparsely clouded, blue sky.Actual size 50 x 70 mm.
IMICRY What looks like butterfly wings or the feathers of an
exotic bird is actually a thin section exposure of prehnite.
Prehnite is an inconspicuous, soft-green mineral, forming radial
crystals inside voids in igneous and metamorphic rocks. In thin
section with transmitted polarized light, the radial crystals of
this mineral take on high order refractive colors. Actual size 18
x 22 mm.
TUR All EHarpoon-like, this large turmaline crystal punctures a matrix of chlorite, which is deposited in the form of
small, rosette-shaped aggregates. Thin section, transmitted
polarized light. Actual size 15 x 20 mm.
OLF
IT Wolframite is the principal ore for tungsten, a
metal used for the manufacture of lamp filaments and other
industrial products. The gleam of spectral colors results from a
wafer-thin veneer of chalcopyrite, which covers the tubular
crystals of the wolframite. Actual size 20 x 25 mm.
AUGITEThis is a thin section exposure, in polarized light, of a
cluster of augite crystals. Augite is a mineral from the pyroxene
group and the individual crystals typically show parallel bands of
internal zoning. Clusters of crystals like these grow out of a central nucleation point and they usually occur in potash rich lava's.
The actual size of this crystal is no more than 8 mm.
CALCIT GLOBULES Calcite is the crystalline variety of
calcium carbonate, a mineral that occurs in many forms. Shells,
4S
corals, limestone and marble are also calcium carbonate. The
globules seen here are formed by radial, crystalline growth in a
void inside lava and they are a rarity. Actual size 40 x 60 mm.
CALCITE 0
FLUORITE Like a stranded space vehicle,
this double-ended crystal of calcite has nested itself on an earlier formed group of fluorite crystals. Quartz was just characterized as the 'ultimate embodiment' of crystallinity, but calcite
comes a close second, as seen in other examples in this chapter.
Actual size 80 x 90 mm.