The Frantz Isodynamic Separator (FIS) separates minerals according to their magnetic susceptibility, and how the individual grains respond to the electromagnetic field versus gravity. It is a high precision, but very slow piece of equipment that is useful for processing and handling small quantities of your sample. It can only work with a grain size between 28 and 200 mesh. Samples larger than 28 mesh will clog the separator.
Principle of operation
: Magnetic properties of minerals : Minerals are classified into four groups based on their attraction to a magnetic field (~magnetic susceptibility), namely:
1. diagmagnetic: repels a magnet, zero dipole moment
2. paramagnetic: random arrangement of magnetic dipoles in a crystal structure; drawn weakly to a magnet.
Example: olivine. 3. ferromagnetic: similar to paramagnetic but has domains that align easily in the presence of an external magnetic field; therefore strongly attracted to a magnet. Example: Fe. 4. ferrimagnetic: antiparallel ionic spin moments; permanent magnetic domains are there. Example: magnetite
The FIS has a chute between the poles of an electromagnet. This chute is partitioned along its length. It can be tilted in two direction: forward (herein called slope), and sideways (herein called tilt). Forward slope controls the speed of movement of the grains down the chute, whereas tilt controls how well the minerals are separated according to their susceptibility. The FIS is typically set up with a slope of 15° and a tilt of 10 – 15° away from the operator. The electric current is then varied to separate the different minerals as they move down the chute.