There would be no bright and colorful fireworks without rocks and minerals.
A firework is produced by launching a shell containing fuel and a color mix high into the air, where it explodes. This explosion propels brightly burning particles in all directions, creating streaks of light in the air.
Combining coal with saltpeter, or potassium-nitrate, creates gunpowder, the most basic fuel used already in ancient China for fireworks. Nitratine, a highly reactive mineral, is the natural form of sodium-nitrate and serves as an oxidizer for fireworks, supporting the fuel’s combustion.
The vibrant colors in a firework don’t come directly from the burning fuel, burning gunpowder results just in a weak yellow, but metallic minerals that are deliberately added to the mix. As the fuel burns, the metal atoms in the crystal structure absorb and release energy, emitting a specific wavelength of light that we perceive as a distinct color.
The element barium produces green light. Barium is obtained from baryte, a barium-sulfate. The baryte group also includes the strontium-sulfate mineral celestite.
Strontium is one of the most abundant elements in the Earth’s crust. However, only two carbonate minerals—celestite and strontianite—contain enough strontium for commercial use. Celestite is named for its occasional delicate blue color and is the principal source for strontium, an element that produces purple light if burned in a firework.
The element calcium will produce yellow light. Named from the Latin word meaning “lime,” calcium is very common in limestone rocks composed of calcite and dolomite.
The elements sodium and cadmium will produce yellow light. Most sodium is obtained nowadays by processing the mineral halite, also known as sodium-chloride or common table salt. Sodium occurs in many other minerals as well, including silicates like amphibole, zeolite and the fluorite mineral cryolite. Cadmium minerals are very rare and include cadmoselite (cadmium-selenide), greenockite (a cadmium-sulfide) and otavite (a cadmium-carbonate). Cadmium substitutes for zinc in sphalerite (zinc-sulfide) and similar minerals, so nowadays most is recovered during the industrial processing of zinc-, copper- and lead-ores.
Burning magnesium and aluminum will emit a bright white light, adding brightness to a firework. Magnesium is found in magnesium-bearing carbonate minerals like dolomite and magnesite. Other less common magnesium minerals are kieserite (magnesium-sulfate) and brucite (magnesium-hydroxide). However, nowadays, most elemental magnesium is obtained by electrolysis of magnesium-chloride, which can be obtained in virtually unlimited quantities from salt water.
Aluminum is the most abundant metallic element in the Earth’s crust and can be obtained from bauxite ore. Bauxite is geologically speaking a sedimentary rock, as it is a mix of minerals like gibbsite, böhmite, and diaspore, and forms by intense weathering of granitic rocks rich in feldspar and mica.
Purple to green light is produced by copper and manganese. Copper is found in many carbonate minerals like azurite and malachite. Other sources for copper are chalcocite, a sulfide named after the Greek word for copper, the copper-silver-sulfide acanthite, and the rare copper-iron-sulfide bornite. Most copper, however, comes from chalcopyrite, a very common copper-iron-sulfide.
Manganese easily reacts with water and air. On Earth, manganese is never found as a free metal, but it is found in a number of minerals. The most important of these minerals is pyrolusite, a mineral consisting essentially of manganese-dioxide and the most important manganese source.
The metallic element cobalt will produce blue light. Cobaltite is a mineral composed of cobalt, arsenic, iron and sulfur. Although rare, it is mined as a significant source of this strategically important metal, as most modern technology will not work without cobalt alloys. Traces of cobalt can be found also in more common minerals like carrollite, a sulfide combining nickel, copper and cobalt, and linnaeite, a cobalt-nickel-sulfide.
