Basic Crystallography

by Ritika

Basic crystallography is about the fundamental principles of geometrical crystallography which are brought in through the medium of symmetry operations, lattices, and the creation of point and space groups.

The study of mineralogy has a fascinating division – Crystallography. One can’t help admiring crystals like pyrite, quartz, or tourmaline which are esthetically pleasing. Crystallography basically means the study of crystals. Crystals refer to all minerals with well-expressed crystal shapes. Crystallographers have been able to get important information about the type and the various stages of formation of crystals through analysis and thus crystallography has become an important branch of science.

Crystallography is divided into 3 sections – geometrical, physical and chemical. Crystal is a standard polyhedral form bound by smooth faces made of chemical compound which forms into a crystal due to the action of inter-atomic forces under specific conditions. Nicholas Steno, a Danish scientist found that irrespective of the conditions in which the crystal grew, the angle of the crystal remains the same. It has been recently proved that this is because of the geometric relationships which retain the structure.

We also find crystals which are not symmetrical in their angles which are quite common and this condition is because of the breakage of minerals. Crystallography proves how during the formation of crystals they get different geometric shapes due to the atomic structure and the conditions under which they form. All crystal forms fit into six crystal systems – Cubic, Tetragonal, Orthorhombic, Hexagonal, Monoclinic, and Triclinic. Most crystals have a center of symmetry even if they don’t have planes of symmetry or axes of symmetry.

Basic crystallography is all about the fundamental principles of geometrical crystallography which are brought in through the medium of symmetry operations, lattices, and the creation of point and space groups. X-ray crystallography shows how spot intensities are bound by the unit cell and various diffraction directions rely on the lattice.

Basic crystallography studies the distribution of atoms in all forms of matter like liquid, gas and any other form.

The different shapes of crystals

• Acicular crystals which are thin needle-like.
• Botryoidal which look like a bunch of grapes
• Crystal Face is one of the flat surfaces of the crystal
• Form which is the group of crystal faces which are alike
• Lamellar which looks like the thin leaves of the book
• Pinacoid which are the crystal faces which are parallel to crystal axes and cut across by the third axis
• First order where the prism is cut by two lateral axes
• Striations where the crystal face has lines.

Talking about the Basic Crystallography Kit used by students, the kit is an efficient screening method for finding out the solubility and starting conditions for the crystallization. The crystallographers investigate a variety of other materials like glasses, fibers, etc. The different methods used by them are: high and low temperature studies, neutron diffraction, high pressure diffraction, electron crystallography, micro gravity experiments, molecular modeling and atomic force microscopy. Crystallographers have recently discovered how proteins recognize the shape of DNA to turn genes on and off.

To have a career as a crystallographer, biology, chemistry, physics, and mathematics are important and any advanced sciences courses will be useful. English and writing skills are also important. At the graduate level, a crystallographer develops and refines a specialty and gains experience on this.

The IUCr is the union adhering to International Council for Science with objectives to promote international cooperation in crystallography, to promote publication of crystallographic research, standardization of methods, units and symbols and relations of crystallography to other sciences.