Help mindat.org|Log In|Register|
Home PageMindat NewsThe Mindat ManualHistory of MindatCopyright StatusManagement TeamContact UsAdvertise on Mindat
Donate to MindatSponsor a PageSponsored PagesTop Available PagesMindat AdvertisersAdvertise on MindatThe Mindat Store
Minerals by PropertiesMinerals by ChemistryRandom MineralSearch by minIDLocalities Near MeSearch GlossaryMore Search Options
Search For:
Mineral Name:
Locality Name:
Keyword(s):
 
The Mindat ManualAdd a New PhotoRate PhotosLocality Edit ReportAdd Glossary Item
StatisticsMember ListBooks & MagazinesMineral Shows & EventsThe Mindat DirectoryHow to Link to MindatDevice Settings
Photo SearchPhoto GalleriesNew Photos TodayNew Photos YesterdayMembers' Photo GalleriesPast Photo of the Day Gallery

Amethyst

Sponsorship for this page has expired!
Formula:
SiO2
Colour:
Violet - purple
Lustre:
Vitreous
Name:
From Greek "a-methystos", meaning not drunk.
A variety of Quartz

A violet to purple variety of quartz.

Amethyst owes its color to gamma irradiation (Berthelot, 1906) and the presence of traces of iron built into its crystal lattice (Holden, 1925). The irradiation causes the iron Fe(+3) atoms that replace Si in the lattice to lose an electron and form a [FeO4]0 color center (Lehmann and Moore, 1966). Despite the intense color, the content of iron occupying Si positions in amethyst is rather low, in the 10-100 ppm range (Dennen and Puckett, 1972).

Changes in color of amethyst by heat treatment and UV radiation. Details on treatment in photo caption.

The color in amethyst from most localities is unevenly distributed in the individual crystals. In amethyst geodes it is often most intense in the growth zones under the rhombohedral faces (at the tips). Occasionally the color is deeper under either the r or z rhombohedral faces, giving the crystal a pinwheel appearence when viewed from the top. In prismatic crystals the color may appear in phantom-like thin layers, while in scepters and skeleton quartz the color is often concentrated along the edges, and accompanied by smoky zones.

When heated to more than about 300-400°C, amethyst loses its violet color and often turns yellow, orange or brown, and then resembles the quartz variety citrine, but depending on the locality and the temperature during the heat treatment it may also turn colorless or - rarely - green (Neumann and Schmetzer, 1984).

Irradiation with UV light will also destroy the color centers, and accordingly prolonged exposure to sunlight will slowly fade amethyst (Currier, 1985). The photo to the right shows the effects of heat (bottom left and right) and UV irradiation (top right) on the color of a specimen from Rio Grande Do Sul.

In general, only the basic crystallographic forms of quartz, the prism and the positive and negative rhombohedra are found on amethyst crystals. Druzy amethyst may lack prism faces. Crystals with additional faces are known only from very few localities.



Visit gemdat.org for gemological information about Amethyst.

Classification of Amethyst

mindat.org URL:
http://www.mindat.org/min-198.html
Please feel free to link to this page.

Occurrences of Amethyst

Geological Setting:
Very common, in many different environments. The commercially most important occurrences are in volcanic rocks, where amethyst crystals outline former gas cavities. In low and medium temperature hydrothermal veins associated with iron ores. As late overgrowth ("scepter quartz") on quartz in pegmatite and alpine-type environments.

Physical Properties of Amethyst

Vitreous
Colour:
Violet - purple
Comment:
pleochroic: blue-violet to purple

Chemical Properties of Amethyst

Formula:
SiO2
Essential elements:
All elements listed in formula:

Relationship of Amethyst to other Species

Other Names for Amethyst

Name in Other Languages:
Basque:Amatista
Bulgarian:Аметист
Catalan:Ametista
Czech:Ametyst
Danish:Ametyst
Dutch:Amethist
Esperanto:Ametisto
Estonian:Ametüst
Finnish:Ametisti
French:Améthyste
Hungarian:Ametiszt
Irish Gaelic:Aimitis
Italian:Ametista
Kazakh (Cyrillic Script):Аметист
Latvian:Ametists
Lithuanian:Ametistas
Norwegian (Bokmål):Ametyst
Polish:Ametyst
Portuguese:Ametista
Romanian:Ametist
Samogitian:Ametėsts
Serbian (Cyrillic Script):Аметист
Simplified Chinese:紫晶
紫水晶
Slovak:Ametyst
Slovenian:Ametist
Spanish:Amatista
Swedish:Ametist
Turkish:Ametist
Ukrainian:Аметист
Wolof:Ametist

Other Information

Health Risks:
No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.

References for Amethyst

Reference List:
Haidinger, W. (1847): Ueber den Pleochroismus des Amethysts. Annalen der Physik, 146, 531-544.

Berthelot, M. (1906): Synthesis of amethyst quartz. Researches on the color, natural or artificial, of some precious stones under radioactive influences. Comp. Rend. Acad. Sci. Paris, 143, 477-488.

Holden, E.F. (1925): The cause of color in smoky quartz and amethyst. American Mineralogist, 9, 203-252.

Frondel, C. (1934): Origin of the segmental coloration of amethyst and smoky quartz. American Museum Novitates, 758, 1-15.

Bappu, M.K.V. (1952): Spectroscopic study of amethyst quartz in the visible region. Indian Journal of Physics, 26, 1-14.

Bappu, M.K.V. (1952): Spectroscopic study of amethyst quartz in the ultraviolet and infrared regions. Indian Journal of Physics, 26, 385-392.

Raman, C.V, Jayaraman, A. (1954): The structure of amethyst quartz and the origin of its pleochroism. Proceedings of the Indian Academy of Sciences, Section A, 40, 189-195.

Cohen, A.J. (1956): Color centers in the α-quartz called amethyst. American Mineralogist, 41, 874-891.

Lietz, J., Munchberg, W. (1957): The coloring of amethyst. II. The effect of ultraviolet and gamma-rays on the coloring. Neues Jahrbuch für Mineralogie, Monatshefte 1957, 25-33.

Chudoba, K.F. (1961): The significance of the color of amethyst. Aufschluss 12, 233-248 (in German).

Chudoba, K.F. (1962): Some relations between the causes of amethyst, smoky quartz, and citrine colors as given by modern science. Mineralogicheskii Sbornik (Lvov), (16), 91-105.

Lehmann, G., Moore, W.J. (1966): Color center in amethyst quartz. Science 152, 1061-1062.

McLaren, A.C., Phakey, P.P. (1966): Electron microscope study of Brazil twin boundaries in amethyst. Physica Status Solidi, 13, 413-422.

Lehmann, G. (1967): Iron color center as the cause of amethyst color. Zeitschrift für Naturforschung, Teil A: Astrophysik, Physik und Physikalische Chemie, 22, 2080-2085.

Dennen, W.H., Puckett, A.M. (1972): On the chemistry and color of amethyst. Canadian Mineralogist 11, 448-456.

Lehmann, G. Bambauer, H.U. (1973): Quartz crystals and their colors. Angewandte Chemie International Edition, 12, 283-290.

Hassan, F., Cohen, A.J. (1974): Biaxial Color Centers in Amethyst Quartz. American Mineralogist 59, 709-718.

Cohen, A.J., Hassan, F. (1974): Ferrous and ferric ions in synthetic alpha-quartz and natural amethyst. American Mineralogist 59, 719-728.

McLaren, A.C., Pitkethly, D.R. (1982): The twinning microstructure and growth of amethyst quartz. Physics and Chemistry of Minerals, 8, 128-135.

Neumann, E., Schmetzer, K. (1984): Mechanism of thermal-conversion of color and color-centers by heat-treatment of amethyst. Neues Jahrbuch für Mineralogie Monatshefte, 6, 272-282.

Balitskii, V.S., Balitskaya, O.V. (1986): The amethyst-citrine dichromatism in quartz and its origin. Physics and Chemistry of Minerals 13, 415-421.

Cohen, A.J. (1985): Amethyst color in quartz, the result of radiation protection involving iron. American Mineralogist 70, 1180-1185.

Currier, R.H. (1985): Natural fading of amethyst. Gems & Gemology, 21(2), 115-116.

Adekeye, J.J.D, Cohen, A.J. (1986): Correlation of Fe4+ optical anisotropy, Brazil twinning and channels in the basal plane of amethyst quartz. Applied Geochemistry, 1, 153-160.

Baran, Z., Godwod, K., Warminski, T. (1987) X-ray study of Brazil twins in natural amethyst. Physica Status Solidi, 101, 9-24.

Kostov, R. (1987): A discussion on the color of amethyst. Priroda (Sofia), 36(2), 10-15.

Schmetzer, K. (1987): Microscopic observation of twinning microstructure in natural amethyst. Neues Jahrbuch für Mineralogie, Monatshefte, 8-15.

Epstein, D.S. (1988): Amethyst mining in Brazil. Gems & Gemmology, 44, 214-228.

Martin, B., Röller, K., Flörke, O.W. (1988): Über die polysynthetische Rechts-Links-Verzwilligung von Amethyst-Quarz und der mikrokristallinen Quarzspezies Chalzedon und Quarzin. Zeitschrift für Kristallographie, Vol.182, 179-180.

Cohen, A.J. (1989): New data on the cause of smoky and amethystine color in quartz. Mineralogical Record 20, 365-367.

Stegger, P., Lehmann, G. (1989) The structures of three centers of trivalent iron in α-quartz. Physics and Chemistry of Minerals, 16, 401-407.

Taijing, L., Sunagawa, I. (1990) Structure of Brazil twin boundaries in amethyst showing brewster fringes. Physics and Chemistry of Minerals, 17, 207-211.

Choh, S.H., Jo, S.H., Song, K.J., Park, I.W., Han, C.S. (1993): Thermal stability of iron(3+) centers in natural and synthetic amethyst. Bulletin of Magnetic Resonance 15, 35-40.

Vasconcelos, P., Wenk, H.R., Rossman, G.R. (1994): The Anahí ametrine mine, Bolivia. Gems and Gemology 30, 4-23.

Rossman, G.R. (1994): The colored varieties of the silica minerals. In: P.J. Haney, ed., Reviews in Mineralogy 29, 433-468.

Lieber, W. (1994): Amethyst - Geschichte, Eigenschaften, Fundorte. Christian Weise Verlag, München.

Balitsky, V.S., Lu, T., Rossman, G.R., Makhina, I.B., Mar'in, A.A., Shigley, J.E., Elen, S., Dorogovin, B.A. (1999): Russian synthetic ametrine. Gems and Gemology 35, 122-134.

Dedushenko, S.K., Makhina, I.B., Mar'in, A.A., Mukhanov, V.A., Perfiliev, Y.D. (2004): What oxidation state of iron determines the amethyst colour? Hyperfine Interactions 156/157, 417-422.

Balzer, R. (2008): Amethyst Uruguay. 304 pp (in German and English).

Tumuklu, A., Gumus, H., Sen, S. (2008): Role of trace elements in natural amethysts in colouring. Asian Journal of Chemistry 20, 4138-4140.

Lameiras, F.S., Nunes, E.H.M., Vasconcelos, W.L. (2009): Infrared and chemical characterization of natural amethysts and prasiolites colored by irradiation. Materials Research, 12, 315-320.

Russo, F.T. (2011): Investigation of optical, electrical and structural properties in Amethyst. Dissertation (Master in Science and Technology of Materials), UNESP, FC, Bauru, 113pp, (in Portugese).

Amethyst: Uncommon Vintage (2012): No. 16 Lithographie. Denver 124pp.

Internet Links for Amethyst

Specimens:
The following Amethyst specimens are currently listed for sale on minfind.com.

Localities for Amethyst

map shows a selection of localities that have latitude and longitude coordinates recorded. Click on the symbol to view information about a locality. The symbol next to localities in the list can be used to jump to that position on the map.
Mineral and/or Locality  
Mindat.org is an outreach project of the Hudson Institute of Mineralogy, a 501(c)(3) not-for-profit organization.
Copyright © mindat.org and the Hudson Institute of Mineralogy 1993-2015, except where stated. Mindat.org relies on the contributions of thousands of members and supporters.
Privacy Policy - Terms & Conditions - Contact Us Current server date and time: August 28, 2015 06:19:32 Page generated: August 26, 2015 15:06:12