Topaz

Topaz is a reddish-yellow and transparent or translucent.

Treatments

When heated, yellow topaz often becomes reddish-pink. The color change upon heating was first discovered by a Parisian jeweler around 1750. In particular the yellow Topaz of Brazil has been known to be treated frequently, by wrapping Topaz in physical vapor deposition, this stone is then sold as 'mystic topaz'.

Localities and occurrence

Topaz is commonly associated with silicic igneous rocks of the cassiterite. It can be found in the Ural and Ilmen mountains, Afghanistan, Czech Republic, Germany, Norway, Pakistan, Italy, Sweden, Japan, Brazil, Mexico, and the United States.

Topaz crystals from Brazilian pegmatites are up to 80 cm x 60 cm x 60 cm in size.^[2] The biggest topaz crystal ever found, named "El Dorado", was found in Brazil in 1984. It weighs 6.2 kg and belongs to the British Royal Collection. The famous Braganza diamond is in most likelihood a Topaz. The Topaz of Aurungzebe, observed by Jean Baptiste Tavernier measured 157.75 carats.^[3]

Etymology and historical and mythical usage

  The name "topaz" is derived from the Greek Τοπάζιος (Τοpáziοs), which was the ancient name of St. John's Island in the Red Sea which was difficult to find and from which a yellow stone (now believed to be olivine) was mined in ancient times; topaz itself (rather than topazios) wasn't really known about before the classical era. ^[4] In the Middle Ages the name topaz was used to refer to any yellow gemstone, but now the name is only properly applied to the silicate described above.

Many modern English translations of the Bible, including the King James Version mention topaz in Exodus 28:17 in reference to a stone in the Hoshen: "And thou shalt set in it settings of stones, even four rows of stones: the first row shall be a sardius, a topaz, and a carbuncle: this shall be the first row." However, since these translations as topaz all derive from the Septuagint translation tòpazi[òs], which as mentioned above referred to a yellow stone that wasn't topaz, probably chrysolite, it should be borne in mind that topaz is not meant here. ^[5] The masoretic text (the Hebrew on which most modern bible translations of the Old Testament are based) has pitdah as the gem the stone is made from; pitdah is of unknown meaning, though scholars think it is related to an Assyrian word meaning flashed. There is a wide range of views among traditional sources about which tribe of the Israelites the stone refers to.

Yellow topaz is the traditional November birthstone, and the state gemstone for the US State of Utah.

References

• Hurlbut, Cornelius S.; Klein, Cornelis, 1985, Manual of Mineralogy, 20th ed., ISBN 0-471-80580-7