Stone of the Week - Amethyst

Amethyst is one of my favorite stones. Well ok, I have a lot of favorite stones – we’ll say this is my favorite purple stone :)

Amethyst in rough form.

Amethyst is actually a type of quartz that has impurities in it that make it this pretty purple color – in the case of amethyst, the impurities are ferric iron. Amethyst can actually change color if exposed to heat – usually to yellow and brown colors, hence sometimes called ‘burnt amethyst’. Sometimes also found with white quartz, and a banded version of alternating white quartz and purple amethyst is refered to as ‘Chevron Amethyst’. The most valued shade of amethyst is a bluish-purple variety called ‘Deep Russian’.

An egg shaped and large crystal of amethyst.

Amethyst is often associated with granites and pegmatites, and can be found in a variety of shapes. The most spectacular is the pointed hexagonal prisms or crystals. A special kind has many tiny crystals that you can’t really see any one crystal, and is commonly sold as ‘fairy amethyst’ though the technical term for it is drusy. It can also be found in geodes, as double terminated crystals (points on both ends), and massive forms.

Amethyst can occur as very pretty crystals. The sample on the right is often called 'fairy amethyst' or drusy amethyst.

Amethyst is the birthstone for Feburary. In metaphysical terms, amethyst is believed to get rid of negativity. Because of the origin of the word Amethyst from the Greek word for ‘not drunken’, many believe that the ancient Greeks and Romans believed it could guard against intoxication, and thus used it to create goblets to hold wine. However a more likely interpretation is that they called the stone amethyst since its color resembled that of wine.

Amethyst is sold in a variety of shapes and sizes for jewelry, including tumbled beads, chips, and freeform stones.

How to tell it from other purple stones: The most other common stone that amethyst is confused with is flourite. Flourite usually appears as a vareity of colors and rarely is sold as just purple. One of the main differences between these two is the hardness - amethyst has a hardness of 7, while flourite has a hardness of just 4 on the Mohs Hardness scale. To tell hardness use objects with a variety of hardnesses to see if the stone can scratch the item or if it scratches the stone (obviously you don't want to do this with your good stones or in a place thats easily seen!). For instance glass has a hardness of 5.5, so flourite wouldn't scratch it but amethsyt would; a coin is 3.5 so both would scratch a coin; a steel knife is 6.5 so would scratch flourite and 'shouldn't' scratch amethyst but it might just a little as impurities in quartz can lower the hardness slightly. Another difference is that flourite occurs as cubic while amethyst is hexagonal (six sides).

Care and Cleaning: Amethyst is not soluble in water, so a damp cloth is safe to use to clean it. To keep it from changing color or lightening, it should be kept away from windows or other sources of heat.


If you have a stone you would like to know about, please feel free to leave a request in the comments section. Have a mystery stone? Leave a link in the comments to a picture of it, and it may be featured as a part of this series!


Amethyst Facts:
Chemical composition: SiO2, ferric iron impurities
Color: Shades of purple
Habit: Commonly 6 sided (hexagonal) prisms, also massive
Fracture: Uneven and conchoidal
Cleavage: None
Luster: Vitreous
Hardness: 7
Specific Gravity: 2.65
Streak: White
Occurrence: Worldwide


References
A Guide to Rocks and Fossils by B. Busbey III, R. R. Coenraads, P. Willis, and D. Roots. Published 2002 by Fog City Press. ISBN: 1877019518

Rocks, Minerals, & Fossils of the World by C. Pellant and R. Phillips. Published 1990 by Little, Brown and Co. ISBN: 0316697966

Wikipedia – Amethyst. http://en.wikipedia.org/wiki/Amethyst