Amethyst is a violet variety of quartz often used in jewelry. The name comes from the Ancient Greek a- ("not") and methustos ("intoxicated"), a reference to the belief that the stone protected its owner from drunkenness; the ancient Greeks and Romans wore amethyst and made drinking vessels of it in the belief that it would prevent intoxication.

Chemistry

Amethyst is the violet variety of quartz; its chemical formula is SiO₂.

In the 20th century, the color of amethyst was attributed to the presence of manganese. However, since it is capable of being greatly altered and even discharged by heat, the color was believed by some authorities to be from an organic source. Ferric thiocyanate was suggested, and sulfur was said to have been detected in the mineral.

More recent work has shown that amethysts' coloration is due to ferric iron impurities. Further study has shown a complex interplay of iron and aluminium is responsible for the color.

On exposure to heat, amethyst generally becomes yellow, and much of the citrine, cairngorm, or yellow quartz of jewelry is said to be merely "burnt amethyst". Veins of amethystine quartz are apt to lose their color on the exposed outcropFact: date=March 2007.

Synthetic amethyst is made to imitate the best quality amethyst. Its chemical and physical properties are so similar to that of natural amethyst that it can not be differentiated with absolute certainty without advanced gemological testing (which is often cost-prohibitive). There is one test based on "Brazil law twinning" (a form of quartz twinning where right and left hand quartz structures are combined in a single crystal) which can be used to identify synthetic amethyst rather easily. In theory however it is possible to create this material synthetically as well, but this type is not available in large quantities in the market.

Composition

Amethyst is composed of an irregular superposition of alternate lamellae of right-handed and left-handed quartz. It has been shown that this structure may be due to mechanical stresses.

Because it has a hardness of seven on the Mohs scale, amethyst is suitable for use in jewelery.

Hue and tone

History

Amethyst was used as a gemstone by the ancient Egyptians and was largely employed in antiquity for intaglios. The Greeks believed amethyst gems could prevent intoxication, while medieval European soldiers wore amethyst amulets as protection in battle.Fact: date=June 2008 Beads of amethyst were found in Anglo-Saxon graves in England.Fact: date=June 2008

A huge geode, or "amethyst-grotto", from near Santa Cruz in southern Brazil was exhibited at the Düsseldorf, Germany Exhibition of 1902.

Mythology

The Greek word "amethystos" may be translated as "not drunken". Amethyst was considered to be a strong antidote against drunkenness, which is why wine goblets were often carved from it. In greek mythology, Dionysus, the god of intoxication, was pursuing a maiden named Amethystos, who refused his affections. Amethystos prayed to the gods to remain chaste, which the goddess Artemis granted and transformed her into a white stone. Humbled by Amethystos's desire to remain chaste, Dionysus poured wine over the stone as an offering, dyeing the crystals purple.