Amethyst

About
Amethyst is a purple variety of quartz (SiO2) and owes its violet color to irradiation, impurities of iron and in some cases other transition metals, and the presence of other trace elements, which result in complex crystal lattice substitutions. The hardness of the mineral is the same as quartz, thus making it suitable for use in jewelry.

Appearance
Amethyst occurs in primary hues from a light pinkish violet color to a deep purple color. Amethyst may exhibit one or both secondary hues, red and blue. High quality amethyst can be found in Siberia, Sri Lanka, Brazil, Uruguay, and the far East. The ideal grade is called "Deep Siberian" and has a primary purple hue of around 75–80%, with 15–20% blue and (depending on the light source) red secondary hues. ‘Rose de France’ is defined by its markedly light shade of the purple, reminiscent of a lavender/lilac shade. These pale colors were once considered undesirable but have recently become popular due to intensive marketing.

Green quartz is sometimes incorrectly called green amethyst, which is a misnomer and not an appropriate name for the material, the proper terminology being prasiolite. Other names for green quartz are vermarine or lime citrine.

Of very variable intensity, the color of amethyst is often laid out in stripes parallel to the final faces of the crystal. One aspect in the art of lapidary involves correctly cutting the stone to place the color in a way that makes the tone of the finished gem homogeneous. Often, the fact that sometimes only a thin surface layer of violet color is present in the stone or that the color is not homogeneous makes for a difficult cutting. It can even cut crystal quartz, which is one of Earth’s sharpest gems.

History
Amethyst was used as a gemstone by the ancient Egyptians and was largely employed in antiquity for intaglio engraved gems.

The Greeks believed amethyst gems could prevent intoxication, while medieval European soldiers wore amethyst amulets as protection in battle in the belief that amethysts heal people and keep them cool-headed. Beads of amethyst were found in Anglo-Saxon graves in England. Anglican bishops wear an episcopal ring often set with an amethyst, an allusion to the description of the Apostles as "not drunk" at Pentecost in Acts 2:15.

A large geode, or "amethyst-grotto", from near Santa Cruz in southern Brazil was presented at a 1902 exhibition in Düsseldorf, Germany.

In the 19th century, the color of amethyst was attributed to the presence of manganese. However, since it can be greatly altered and even discharged by heat, the color was believed by some authorities to be from an organic source. Ferric thiocyanate has been suggested, and sulfur was said to have been detected in the mineral.

Value
Up until the 18th century, amethyst was included in the cardinal, or most valuable, gemstones (along with diamond, sapphire, ruby, and emerald). However, since the discovery of extensive deposits in locations such as Brazil, it has lost most of its value.

Collectors look for depth of color, possibly with red flashes if cut conventionally. As amethyst is readily available in large structures the value of the gem is not primarily defined by carat weight; this is different from most gemstones where the carat weight exponentially increases the value of the stone. The biggest factor in the value of amethyst is the color displayed.

The highest-grade amethyst (called "Deep Russian") is exceptionally rare and therefore, when one is found, its value is dependent on the demand of collectors. It is, however, still orders of magnitude cheaper than the highest-grade sapphires or rubies.

Record(s)
Named The Empress of Uruguay, this is the largest Amethyst Geode in the world. Standing a staggering 3.27 meters tall, the geode weighs 2.5 tonne! Each of the thousands of perfect crystals was formed inside the geode exactly as you see them now, 130 millions years ago.