other names: Magnesium aluminate
mineral class: Oxides and hydroxides
chemical formula: MgAl2O4
Chemical elements: Magnesium, aluminum, oxygen
Similar minerals: Magnetite
colour: red, pink, green, blue, purple, yellow, white
shine: Glass gloss
crystal structure: cubic
mass density: 3,7
magnetism: not magnetic
Mohs hardness: 7 - 8
stroke color: White
transparency: transparent to opaque
General information about spinel:
spinel describes, on the one hand, a mineral that appears in many colors, which is counted among the oxides and hydroxides, and, on the other hand, a group of minerals, which include gahnite, galaxite, magnetite and hercynite. Its name is probably derived from the Latin "spinella" for "little ones" and refers to its octahedral and pointed crystals. These actually look very much like small thorns in appearance. But it is also possible that the name spinel from the Greek word "spinnos" developed, which translates as "sparkle" or "spark" means.
Spinel may appear in many different colors depending on composition and chemical additives. Above all, the effect of chromium, copper, iron or zinc results in numerous color variants. Therefore, several names are distinguished in the trade, which relate to the color of the respective stones. For example, green spinel is known as chlorospinell, bright red stones are known as balas rubies, and dark green specimens rich in iron are named Ceylanit or Pleonast. Spinel may also appear in pink, orange, violet, different shades of blue as well as in brown, yellow and colorless.
Due to the bright colors, its high Mohs hardness of up to 8 and its low cleavage, spinel is considered to be easy to process and at the same time coveted gemstone. Its transparency ranges from nearly opaque to completely transparent, the line color is always white. The mineral is from uneven to shell-like or splintery breakage and has a glassy shine. It forms massive to granular aggregates and reacts acids and heat to insensitive.
Origin and occurrence:
Spinel is formed in magmatic or metamorphic, strongly basic rock such as gneiss, basalt or marble. Association with corundum, magnetite and andalusite is frequently observed. Spinels are found worldwide and mined in over 1,400 deposits. However, precious spinel, which is highly sought after in the jewelery industry, is mined mainly in Myanmar (Burma), Tanzania, Afghanistan and Sri Lanka. Greenland, Norway, Scotland and Ireland, Germany and Austria, Russia, Morocco, Madagascar, China and Japan are also some of the countries where the sites are located.
Use by humans:
Transparent and flawless, intensely colored spinels are extremely rare and are due to their strong shine as coveted gemstones, which achieve high prices. Noble spins therefore adorn the crown jewels of many royal families and are internationally famous. These include, for example, the Black Prince's Ruby and the Timur Ruby, both owned by the British Royal Family. To obtain a more intense color and transparency, spinels are often fired in the jewelry industry. Since the mineral has a very high melting point of over 2100 degrees Celsius, it is also used in the manufacture of refractory, needed in the industry vessels used today, but only more synthetically produced spinels are used.