BISMUTH
Ohh, science...
Bismuth is a brittle metal with a white, silver-pink hue, often occurring in its native form, with an iridescent oxide tarnish showing many colors from yellow to blue. The spiral, stair-stepped structure of bismuth crystals is the result of a higher growth rate around the outside edges than on the inside edges. The variations in the thickness of the oxide layer that forms on the surface of the crystal causes different wavelengths of light to interfere upon reflection, thus displaying a rainbow of colors. When burned in oxygen, bismuth burns with a blue flame and its oxide forms yellow fumes. Its toxicity is much lower than that of its neighbors in the periodic table, such as lead, antimony, and polonium.
No other metal is verified to be more naturally diamagnetic than bismuth. (Superdiamagnetism is a different physical phenomenon.) Of any metal, it has one of the lowest values of thermal conductivity (after manganese, and maybe neptunium and plutonium) and the highest Hall coefficient. It has a high electrical resistance. When deposited in sufficiently thin layers on a substrate, bismuth is a semiconductor, despite being a post-transition metal.
Elemental bismuth is denser in the liquid phase than the solid, a characteristic it shares with antimony, germanium, silicon and gallium. Bismuth expands 3.32% on solidification; therefore, it was long a component of low-melting typesetting alloys, where it compensated for the contraction of the other alloying components, to form almost isostatic bismuth-lead eutectic alloys.
Though virtually unseen in nature, high-purity bismuth can form distinctive, colorful hopper crystals. It is relatively nontoxic and has a low melting point just above 271 °C, so crystals may be grown using a household stove, although the resulting crystals will tend to be lower quality than lab-grown crystals.
At ambient conditions bismuth shares the same layered structure as the metallic forms of arsenic and antimony, crystallizing in the rhombohedral lattice (Pearson symbol hR6, space group R3m No. 166), which is often classed into trigonal or hexagonal crystal systems. When compressed at room temperature, this Bi-I structure changes first to the monoclinic Bi-II at 2.55 GPa, then to the tetragonal Bi-III at 2.7 GPa, and finally to the body-centered cubic Bi-IV at 7.7 GPa. The corresponding transitions can be monitored via changes in electrical conductivity; they are rather reproducible and abrupt, and are therefore used for calibration of high-pressure equipment.
YOU CAN MAKE YOUR OWN BISMUTH CRYSTAL
Bismuth is one of the easiest and prettiest metal crystals that you can grow yourself. The crystals have an interesting geometric hopper form and are rainbow-colored from the oxide layer that quickly forms on them. Try these step-by-step instructions for growing bismuth crystals.
MATERIALS YOU NEED
▲bismuth
▲2 stainless steel measuring cups or aluminum cans that you have cut in half to make shallow bowls
▲a stove, hot plate, or propane torch
You have a few different options for obtaining bismuth. You can use non-lead fishing sinkers (for example, Eagle Claw makes non-lead sinkers using bismuth), you can use non-lead ammunition (the shot will say it is made from bismuth on the label), or you can buy bismuth metal. The quality of crystals you obtain depends in part on the purity of the metal, so make sure you are using bismuth and not an alloy. One way to be certain of the purity is to remelt a crystal of bismuth. It can be used over and over again.
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