Amethyst

The purple variety of quartz, amethyst ranges from pale lilac to deep violet, its color arising from iron impurities combined with natural irradiation inside the crystal. One of the most widely used gemstones anywhere, and a moderately priced semi-precious stone, it occurs in alluvial deposits and geodes across Brazil, Uruguay, Zambia, and Russia. It crystallizes in the trigonal system and measures 7.0 on the Mohs scale, hard enough for everyday wear. Historically tied to sobriety and royalty, amethyst adorned the crowns of European monarchs and the rings of Catholic bishops for centuries, and it remains the birthstone for February.

Physical & Optical Properties

Category Semi-Precious Gems

Mohs Hardness 7.0

Specific Gravity 2.65

Refractive Index 1.544 – 1.553

Crystal System Trigonal

Cleavage None

Fracture Conchoidal

Color purple

Birefringence 0.009

Dispersion 0.013

Pleochroism Weak: (gray)-purple - reddish-purple

Mohs Hardness

Mohs hardness of Amethyst shown against the ten reference minerals, from talc (1) to diamond (10).

Mohs	Reference mineral	Amethyst
1	Talc
2	Gypsum
3	Calcite
4	Fluorite
5	Apatite
6	Orthoclase
7	Quartz	●
8	Topaz
9	Corundum
10	Diamond

Crystal System

Value & Market

Price Tier Moderate ($50-500/ct)

Where to Buy Amethyst

Blue Nile Fine jewelry retailer

James Allen Gemstone jewelry

Brilliant Earth Ethically sourced gems

Amazon Wide selection

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Cultural Significance

Birthstone Month 2 (modern)

Treatments

Heat treatment between 878 - 1382 degrees F (470 - 750 degrees C) produces light yellow, red-brown, green, or colorless varieties. The original color an be restored by X-ray radiation. - Gemstones of the world, Walter Schumann, 2001, p 118 Synthetic amethyst produced by hydrothermal method entered the market in 1970s. 7Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) 2.65Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004) BrittleWalter Schumann, Gemstones of the world (2001) Very brittle NoneWalter Schumann, Gemstones of the world (2001) ConchoidalWalter Schumann, Gemstones of the world (2001) The colour does not resist high temperatures. When subjected to the action of heat it changes first to a more or less pronounced yellow, gradually assumes a greenish shade, and finally disappears.Max Bauer, Precious Stones (1968) Dover Publications 1.544 to 1.553Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) 0.009Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004) Weak: (gray)-purple - reddish-purpleHerve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) 0.013Walter Schumann, Gemstones of the world (2001) Purple, violet, pale red-violetWalter Schumann, Gemstones of the world (2001) More from other references Some amethysts lose some color in daylight.Walter Schumann, Gemstones of the world (2001) ReddishHerve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) Violet to purple, O2+→Fe4+ charge transfer, due to irradiation.W. William Hanneman, Pragmatic Spectroscopy For Gemologists (2011) Transparent,TranslucentUlrich Henn and Claudio C. Milisenda, Gemmological Tables (2004) Inert to weak greenish or bluishHerve Nicolas Lazzarelli, Blue Chart Gem Identification (2010) TrigonalUlrich Henn and Claudio C. Milisenda, Gemmological Tables (2004) Hexagonal prismsWalter Schumann, Gemstones of the world (2001) Found in geodes in alluvial deposits.Walter Schumann, Gemstones of the world (2001) Amethyst information at mindat.org Bolivia  Laurs (2001, 2010) Laurs (2001, 2010) Laurs (2001, 2010) Brazil  Couto (2000) Priester (1999) Rocks & Min.:5:131. Rocks & Min.: 5:131. Rocks & Min.:5:131. Balzer (1999) R. Batista and D. Epstein (2000) Cambodia  Ngu and Ngoc (1986) Canada  Garland (2004) Sinkankas (1997) Sinkankas (1997) India  S. Fernandes (1999) Kenya  Henn and Milisenda (2001) Madagascar  Aurisicchio et al. (1999) Madagascar, extraLapis English No.1, 2001, p. 44 Pezzotta (1999) Madagascar - extraLapis English No.1, p. 92 Mexico  Ontiveros et al. (2004) Ontiveros et al. (2004) Myanmar  Ted Themelis (2008) Gems & mines of Mogok Ted Themelis (2008) Gems & mines of Mogok Ted Themelis (2008) Gems & mines of Mogok Namibia  Michelou (2006) Nigeria  Laurs and Koivula (2003) Peru  Russia  P. Lyckberg (2009) V. Bukanov (1999) V. Bukanov (1999) South Korea  Yang et al. (2001) Sri Lanka  Uruguay  Gilg et al. (2003) mindat.org USA  Lowell and Koivula (2004) Laurs (2005)

About Amethyst

Amethyst is the purple variety of quartz, ranging from pale lilac to deep violet, with color caused by iron impurities and natural irradiation within the crystal lattice. One of the most popular and widely used gemstones in the world, it is found in alluvial deposits and geodes across Brazil, Uruguay, Zambia, and Russia. Historically associated with sobriety and royalty, amethyst adorned the crowns of European monarchs and the rings of Catholic bishops for centuries.