Alum Octahedron and Cluster, both grown using the supercooling method.
These crystals of Alum are cubic in structure, and grown into the ideal form of an octahedron. Diamond is of the cubic form and also grows into the octahedron.
How does cubic become an octahedron? It all has to do with the growth rates of the crystalline faces. Here's a two-dimensional representation. The faces of the cube grow faster than the corners. Also, see how the cubes remain in the octahedron.
Nickel Sulfate Crystal (supercooling) and Clusters grown first by supercooling and then by evaporation. Note the bigger crystals on the evaporation method grown crystals.
The form of Nickel Sulfate is tetragonal. Rutile (shown in the intro as inclusions in quartz) is also tetragonal. The form of rutile is shown below. A material that is also tetragonal, phosgenite, which looks more like the Nickel Sulfate is shown after the rutile.
Sodium Chlorate Crystals (which are or the cubic system) grown by supercooling and by evaporation. Note that the evaporation crystal is clearer (and somewhat smaller).
The classic pyrite is also cubic and one of its many growing forms is cubic. Shown below.
Sodium Nitrate clusters that were grown by supercooling. A crystal that was grown by evaporation. Neither set turned out very well, although the rhombohedron shape is seen on the evaporation crystal (a la calcite). Its structure is trigonal
Calcite is a trigonal crystal that grows in the same shape (and possesses the same optical and cleavage properties as Sodium Nitrate). Shown below. This same crystal is used in the optical birefringence demonstration later.
Trigonal? You say. Yes, trigonal. Look at this calcite crystal below that has its trigonal symmetry displayed. See if you can see this same symmetry in the calcite crystal above.
Potassium Ferricyanide crystals grown by the evaporation method. Small but nicely formed. Could have been bigger with more time. This crystal is monoclinic.
Spodumene (of which the native-NC mineral hiddenite is a variety) is monoclinic as well. Crystal shown below.
Calcium Copper Acetate cluster that was grown using the evaporation method. These crystals are of the tetragonal system, like Nickel Sulfate, rutile, and phosgenite above.
Rochelle Salt crystals, which have orthorhombic crystalline structure, grew well under either method. Here's a picture of the one used for the piezoelectricity experiment grown using the supercooling method.
Here's another crystal grown by the supercooling technique. Next, a crystal grown by evaporation shown at two angles. In the second angle, the loop of floss that was holding the seed crystal is clearly seen.
Tanzanite, a blue-violet mineral from Africa, is also of the orthorhombic system. Shown below.
Epsom Salt grew too quickly when trying to use supercooling technique and produced a crystalling ooze within a half-hour.
Copper Acetate failed to produce crystals using the evaporation or supercooling method. Here's a picture of the solution that failed to produce. Its crystalline system would have been monoclini, like the Potassium Ferricyanide and spodumene, above.
Monoammonium Phosphate didn't do much with evaporation, but grew well with supercooling (grown in the bottom of a 2-liter soda bottle with the tope cut off).
It was unclear which system these crystals belonged to. Although, judging by the rectangular cross section of the crystals and their elongated nature, the system might be orthorhombic, like rochelle salt. Of course, the end product looks different.