X-Ray Diffraction Laboratory
The department houses a laboratory for study of
minerals and crystalline substances using X-ray diffraction techniques.
Because the wavelength of X-rays are similar to the spacing of atoms in
crystals, X-rays are scattered by crystals in much the same way that a
diffraction grating scatters light. Discrete angles and intensities of
scattering correlate with the geometric pattern of atoms within a
crystal. Examination of the pattern and intensities of scattering from
a sample are used to interpret its crystal structure and to identify
the mineral or crystalline compound constituting the sample.
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Our X-ray diffraction facilities are used to
identify minerals in specimens within the collections and crystalline
substances in experimental syntheses from other laboratories. In
addition, the facilities are used by the conservation lab and other
departments to identify such things as pigments in paints, degradation
products on artifacts, and minerals in fossils. The primary facility
for this a Philips PW-1710 automated powder diffractometer attached to
a 2000 watt Cu X-ray source (photo on left) and controlled by a PC. In
addition Gandolfi cameras are used to examine minute crystals or
crystal fragments. |
| A single crystal
diffractometer is used to determine the basic geometry, called the
space group and lattice parameters, of individual crystals, as well as
the crystal structure � the positions of atoms in the crystal lattice.
The crystal structure is the most fundamental characteristic of
crystalline matter. The diffractometer (photo on right) consists of
2000-watt molybdenum (Mo) X-ray source and a 3-circle Picker goniostat
(the green unit in the photograph which controls the crystal
orientation and X-ray detector/scintillator) controlled by a computer
with PCXTAL software. |
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