OliT Chiastolite is a unique variety of the mineral
Andalusite, an aluminum silicate. Chiastolites are columnar, prismatic crystals of this mineral, with dark inclusions of carbon or
clay particles, which are arranged in the form of a cross.
Chiasma is Greek for cross. This picture is of a thin section cut
squarely across such an elongated crystal column. Diameter ±
45mm.
,..ALENt E Much like contour lines on a map, crystal-growth
patterns (see 'Striations', hereunder) accentuate the surface of a
small specimen of galenite, a common lead-ore. Actual size 40 x
50mm.
ACQU p
Seen here in cross section are beds of
sand and gravel deposited in a Holocene fluviatile environment
in the Netherlands. Cross bedding, ripple marks and other
structures typical for such river deposits are very distinctly displayed.This section is characteristic for the way geology is practised in the predominantly young and unlithified sediments of
Holland. It is a 'lacquer profile', prepared by immersing a clean
cut, vertical section of such sediments, for example in a sand- or
gravel-pit, with lacquer. After the lacquer has hardened the section is carefully peeled off and fastened to a board. The width of
this section is nearly one meter.
ST I TIO S Striations and other striped patterns sometimes seen on crystal planes are a telling indication of how crystals grow, layer-by-Iayer. See also previous page. This example is
on the face of a pyrite-cube. Actual size 17 x 22 mm.
GR PHIC GR N TE Granite is formed at great depth, by
the solidification of magma. Graphic granite is a particular variety, in which the two essential rock forming minerals, quartz and
feldspar, have solidified eutectically (simultaneously). This results
in an orderly pattern: the quartz takes on the shape of hieroglyphs and is embedded in a matrix of patchy, monocrystalline
feldspar.
T Ie
L This cut and polished slab of lead ore,
typical for certain ancient mining districts in Germany and
Belgium, shows a remarkable skeletal pattern, which results
from the intergrowth of zinc in the lead ore.The Germans refer
to this pattern as 'gestrickt' (knitted), hence the striking name
they give to this type of ore. Actual size 100 x 150 mm.
III
Andalusite, an aluminum silicate. Chiastolites are columnar, prismatic crystals of this mineral, with dark inclusions of carbon or
clay particles, which are arranged in the form of a cross.
Chiasma is Greek for cross. This picture is of a thin section cut
squarely across such an elongated crystal column. Diameter ±
45mm.
,..ALENt E Much like contour lines on a map, crystal-growth
patterns (see 'Striations', hereunder) accentuate the surface of a
small specimen of galenite, a common lead-ore. Actual size 40 x
50mm.
ACQU p
Seen here in cross section are beds of
sand and gravel deposited in a Holocene fluviatile environment
in the Netherlands. Cross bedding, ripple marks and other
structures typical for such river deposits are very distinctly displayed.This section is characteristic for the way geology is practised in the predominantly young and unlithified sediments of
Holland. It is a 'lacquer profile', prepared by immersing a clean
cut, vertical section of such sediments, for example in a sand- or
gravel-pit, with lacquer. After the lacquer has hardened the section is carefully peeled off and fastened to a board. The width of
this section is nearly one meter.
ST I TIO S Striations and other striped patterns sometimes seen on crystal planes are a telling indication of how crystals grow, layer-by-Iayer. See also previous page. This example is
on the face of a pyrite-cube. Actual size 17 x 22 mm.
GR PHIC GR N TE Granite is formed at great depth, by
the solidification of magma. Graphic granite is a particular variety, in which the two essential rock forming minerals, quartz and
feldspar, have solidified eutectically (simultaneously). This results
in an orderly pattern: the quartz takes on the shape of hieroglyphs and is embedded in a matrix of patchy, monocrystalline
feldspar.
T Ie
L This cut and polished slab of lead ore,
typical for certain ancient mining districts in Germany and
Belgium, shows a remarkable skeletal pattern, which results
from the intergrowth of zinc in the lead ore.The Germans refer
to this pattern as 'gestrickt' (knitted), hence the striking name
they give to this type of ore. Actual size 100 x 150 mm.
III