There were numerous examples of crystalline bodies that had no saline properties, e.g. metals. Both zinc and bismuth could be obtained as crystals, and gold,
silver and iron could show beautiful crystals at the surface.
Hooykaas has pointed out that Haüy is credited as the founder of crystallography
based on his influential publications of 1784 [30] and 1801 [31], while it in fact is
important to pay attention to Haüy’s first two essays on crystallography, which
were read before the French Academy of Sciences in February and December 1781,
respectively [24].
Haüy’s original publication is based on lamellae in a similar fashion as in
Bergman’s work, and these lamellae did not necessarily have the same size. On the
other hand, he corrected Bergman on several important points: he criticised
Bergman for using identical primitive forms for calcite and garnet, he criticised
Bergman’s truncation of lamellae and his ignorance of the angles between crystal
faces. Unlike Bergman, Haüy’s theory relied more heavily on cleavage (but striation was used to indicate potential cleavage planes in hard crystals). He did not
attempt to relate chemically unrelated crystals to each other and he paid closer
attention to the angles between faces than Bergman did. For instance, the garnet
was based on a regular rhombic dodecahedron is Haüy’s system. This may partly be
due to the fact that Haüy had a larger supply of crystals to study and base his theory
on compared with Bergman who only studied naturally occurring minerals [32].
It was in 1784 that Haüy put forward a theory that would lay the foundation for
modern crystallography. Haüy now proposed a system where a crystal was built up
by stacking rhombohedral “crystal molecules” (molécules intégrantes), i.e. unit
cells. These were stacked in rows, and as the crystal grew, rows could be omitted
giving rise to different habits but always with the same inclination between faces.
In his 1784 essay, Haüy gave the impression that this theory was not new, but
dated back to his original essays from 1781 and that it was solely his own invention
[24]. However, as pointed out by Hooykaas, as he had not criticised Bergman’s
relation of hyacinth and garnet to Iceland spar in his original paper, this cannot be
true. Actually, the very fact that he based his 1781 discussion on Iceland spar and
garnet points directly to Bergman as his source of inspiration, since the only
connection between these minerals is Bergman’s theory. Haüy also constantly, and
according to Hooykaas deliberately, referred to “Bergman’s paper of 1779”, rather
than 1773, giving the impression that Bergman’s publication appeared 6 years later
than it actually did [24]. In his 1801 book, Haüy clearly stated that his original idea
was to device crystal form from “crystal molecules”. In Hooykaas words: “Haüy, as
the creator of a new revolutionary theory, had a tendency to belittle his predecessors
and forget his debts to them. He could not bear that anything should be detracted
from his theory. This peculiarity does not necessarily imply dishonesty but it means
that his sight was not very clear when it came to consideration of his own
development”.
Another French mineralogist, Romé de l’Isle (1736–1790) put forward another
important theory of crystallography in 1783, the law of constant angles between
crystal faces, a theory anticipated by Nicholas Steno 100 years earlier. Unlike
Bergman, de l’Isle based his theory on exact measurements on angles, and was
352
25 Bergman’s Contributions to Mineralogy
silver and iron could show beautiful crystals at the surface.
Hooykaas has pointed out that Haüy is credited as the founder of crystallography
based on his influential publications of 1784 [30] and 1801 [31], while it in fact is
important to pay attention to Haüy’s first two essays on crystallography, which
were read before the French Academy of Sciences in February and December 1781,
respectively [24].
Haüy’s original publication is based on lamellae in a similar fashion as in
Bergman’s work, and these lamellae did not necessarily have the same size. On the
other hand, he corrected Bergman on several important points: he criticised
Bergman for using identical primitive forms for calcite and garnet, he criticised
Bergman’s truncation of lamellae and his ignorance of the angles between crystal
faces. Unlike Bergman, Haüy’s theory relied more heavily on cleavage (but striation was used to indicate potential cleavage planes in hard crystals). He did not
attempt to relate chemically unrelated crystals to each other and he paid closer
attention to the angles between faces than Bergman did. For instance, the garnet
was based on a regular rhombic dodecahedron is Haüy’s system. This may partly be
due to the fact that Haüy had a larger supply of crystals to study and base his theory
on compared with Bergman who only studied naturally occurring minerals [32].
It was in 1784 that Haüy put forward a theory that would lay the foundation for
modern crystallography. Haüy now proposed a system where a crystal was built up
by stacking rhombohedral “crystal molecules” (molécules intégrantes), i.e. unit
cells. These were stacked in rows, and as the crystal grew, rows could be omitted
giving rise to different habits but always with the same inclination between faces.
In his 1784 essay, Haüy gave the impression that this theory was not new, but
dated back to his original essays from 1781 and that it was solely his own invention
[24]. However, as pointed out by Hooykaas, as he had not criticised Bergman’s
relation of hyacinth and garnet to Iceland spar in his original paper, this cannot be
true. Actually, the very fact that he based his 1781 discussion on Iceland spar and
garnet points directly to Bergman as his source of inspiration, since the only
connection between these minerals is Bergman’s theory. Haüy also constantly, and
according to Hooykaas deliberately, referred to “Bergman’s paper of 1779”, rather
than 1773, giving the impression that Bergman’s publication appeared 6 years later
than it actually did [24]. In his 1801 book, Haüy clearly stated that his original idea
was to device crystal form from “crystal molecules”. In Hooykaas words: “Haüy, as
the creator of a new revolutionary theory, had a tendency to belittle his predecessors
and forget his debts to them. He could not bear that anything should be detracted
from his theory. This peculiarity does not necessarily imply dishonesty but it means
that his sight was not very clear when it came to consideration of his own
development”.
Another French mineralogist, Romé de l’Isle (1736–1790) put forward another
important theory of crystallography in 1783, the law of constant angles between
crystal faces, a theory anticipated by Nicholas Steno 100 years earlier. Unlike
Bergman, de l’Isle based his theory on exact measurements on angles, and was
352
25 Bergman’s Contributions to Mineralogy