Ametrine, also known as trystine, golden amethyst, or by the trade name bolivianite, is a variety of

quartz Quartz is a hard, crystalline mineral composed of silica (silicon dioxide). The Atom, atoms are linked in a continuous framework of SiO4 silicon–oxygen Tetrahedral molecular geometry, tetrahedra, with each oxygen being shared between two tet ...

with alternating zones of purple and yellow-orange coloration. Its name is a portmanteau of

amethyst Amethyst is a Violet (color), violet variety of quartz. The name comes from the Koine Greek from - , "not" and (Ancient Greek) / (Modern Greek), "intoxicate", a reference to the belief that the stone protected its owner from Alcohol into ...

and citrine. While ametrine is commonly referred to as a combination of these two quartz varieties, some sources claim this is not accurate. Almost all commercially available ametrine is mined in

Bolivia Bolivia, officially the Plurinational State of Bolivia, is a landlocked country located in central South America. The country features diverse geography, including vast Amazonian plains, tropical lowlands, mountains, the Gran Chaco Province, w ...

Color

Ametrine, as its name suggests, is commonly believed to be a combination of citrine and amethyst in the same crystal. However, sources do not agree that the yellow-orange quartz component of ametrine may properly be called citrine. Like the purple color of amethyst, the yellow color in ametrine originates from trace amounts of

iron Iron is a chemical element; it has symbol Fe () and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, forming much of Earth's o ...

in the crystal structure. The difference in coloration is due to the iron existing in different

oxidation states In chemistry, the oxidation state, or oxidation number, is the hypothetical charge of an atom if all of its bonds to other atoms are fully ionic. It describes the degree of oxidation (loss of electrons) of an atom in a chemical compound. Concep ...

. The yellow segments have been oxidized by heat, while the amethyst segments remain unoxidized. Some sources define citrine solely as quartz with its color originating from

aluminum Aluminium (or aluminum in North American English) is a chemical element; it has chemical symbol, symbol Al and atomic number 13. It has a density lower than that of other common metals, about one-third that of steel. Aluminium has ...

-based color centers, similar to those of smoky quartz. This definition excludes any amethyst that has been oxidized by heat. Accordingly, the yellow quartz in ametrine would not be considered true citrine.

Origin

Naturally-occurring ametrine is sourced almost exclusively from a single mine in Bolivia. Deposits also exist in Brazil and India. The different oxidation states occur due to there being a

temperature Temperature is a physical quantity that quantitatively expresses the attribute of hotness or coldness. Temperature is measurement, measured with a thermometer. It reflects the average kinetic energy of the vibrating and colliding atoms making ...

gradient across the crystal during its formation. However, most ametrine on the market is created by partially heating or irradiating amethyst. Ametrine in the low price segment may stem from synthetic material. Green-yellow or golden-blue ametrine does not exist naturally. Synthetic ametrine is grown with the hydrothermal method using solutions doped with specific elements, followed by irradiation of the created crystals.

Structure

Ametrine is composed of

silicon dioxide Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , commonly found in nature as quartz. In many parts of the world, silica is the major constituent of sand. Silica is one of the most complex and abundan ...

(SiO₂) and it is a

tectosilicate Silicate minerals are rock-forming minerals made up of silicate groups. They are the largest and most important class of minerals and make up approximately 90 percent of Earth's crust. In mineralogy, the crystalline forms of silica (silicon dio ...

, which means it has a silicate framework linked together through shared oxygen atoms.

History

Legend has it that ametrine was first introduced to

Europe Europe is a continent located entirely in the Northern Hemisphere and mostly in the Eastern Hemisphere. It is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west, the Mediterranean Sea to the south, and Asia to the east ...

by a conquistador's gifts to the

Spanish Spanish might refer to: * Items from or related to Spain: **Spaniards are a nation and ethnic group indigenous to Spain **Spanish language, spoken in Spain and many countries in the Americas **Spanish cuisine **Spanish history **Spanish culture ...

Queen in the 1600s, after he received a mine in

as a

dowry A dowry is a payment such as land, property, money, livestock, or a commercial asset that is paid by the bride's (woman's) family to the groom (man) or his family at the time of marriage. Dowry contrasts with the related concepts of bride price ...

when he married a princess from the native Ayoreos tribe.Vasconcelos, Paolo; Wenk, Hanz-Rudolf; Rossman, George. "The Anahí Ametrine Mine, Bolivia," Gems and Gemology, Spring 1994, p. 4-23

References

External links