Rhenium is a lustrous silvery-white metal. Rhenium powder is black or dark-gray, depending on the dispersion. It is one of the densest and solid metals (density - 21.02g/cm³). Melting point - 3459K (3186 °C). Boiling point - 5869K (5596 °C). Paramagnetic.
Rhenium has a hexagonal crystal structure a = 276.1 pm and c = 445.6 pm.

Germanium, Ge (from the Latin. Germania - Germany* a. Germanium; n. Germanium; f. Germanium; i. Germanio) - a chemical element of the fourth group of the periodic system, atomic number 32, atomic mass 72.59. Natural germanium consists of 4 stable isotopes 70Ge (20.55%), 72Ge (27.37%), 73Ge (7.67%), 74Ge (36.74%) and one radioactive 76Ge (7,67%) with a half-life of 2•106 years. It was discovered in 1886 by the German chemist K. Winkler in the mineral argyrodite; predicted by D. N. Mendeleev (ekasilicon) in 1871.

Rhodium is one of the rarest and most valuable precious metals of the platinum group, discovered at the beginning of the 19th century and named “rose” in translation from ancient Greek. The scientist, who first discovered rhodium, managed to isolate bright pink powder in native platinum solution, which was transformed into a heavy metal of silver color. And since the amount of rhodium in platinum was minimal and was calculated only in fractions of a percent, this metal became one of the rarest, most valuable and unattainable. No wonder that the price of rhodium was several times higher and still exceeds the price of gold.

Ruthenium is an element of the eighth group of the fifth period of the periodic table of chemical elements, its atomic number is 44. Elementary ruthenium is a transitional metal of silver color. It refers to platinum metals.

Indium is a silvery-white soft metal. Its crystal structure is tetragonal face-centered with the following parameters: a=0.4583pm, c=0.4936pm. The density of indium is 7310 kg/m3. Indium is malleable, its melting point is 156.78°С, boiling point is 2024°С; specific heat at 0-150°С 234.461 J/kg•К, Young 's modulus - 11GPa, Brinell hardness - 9MPa. The oxidation degree is +3, occasionally +1 and +2.