What a beautiful stone, what a color! The February birthstone can be pale or dark and all the shades in between. It can be expensive or inexpensive. Some stones can exhibit a color change from red purple to blue purple depending on the lighting, and amethyst can occur in a number of different ways.
A form that regularly astonishes those just becoming acquainted with amethyst, are the sometimes very large geodes (hollow stones) or "Cathedrals" as they are called in Rock Shops. I love to see the reaction of those who've never seen them before. They behold a hollow in the stone that absolutely bristles with sparkling deep purple crystal points. They see it as an extravagant wonder of nature, and that is just what it is. In an old stockpile of gems I discovered a fairly uncommon type of amethyst from Mexico. The crystals had a frothy white coating of quartz. When cut in cross section the crystals showed a very pleasant purple in the center surrounded by a rich Smoky Quartz overlaid by Milky Quartz on the outside. I faceted a stone from the parcel and it turned out to be a very respectable triangular stone which sat well with the others I had finished from other places. It's been a few years since I cut that particular piece and now, in retrospect, I think the best way to cut this variety, if possible, would be to simply flat polish both sides of those wonderful slices and let them tell the story of it's formation.
I also found something called, originally, Phantom Amethyst. They now sell this material as Chevron Amethyst. It is from Africa, probably Zambia, and it is known for exhibiting a strong "zoning". Zoning in amethyst refers to a tendency it has for producing a deep purple band beside a weak purple or white band. This is normally thought of as a flaw in amethyst, because uneven color in a stone is just not very attractive. However in Chevron Amethyst it becomes an advantage, because we are delighted to find in the material a lot of very geometric shapes and patterns in alternating purple and white. In the Ural Mountains of Russia during the reign of Catherine the Great, amethyst was discovered that set the standard. The crystals were large and of a deep, rich purple. When cut, the stones would exhibit the "red flash" which has become so highly desirable in good amethyst. Because of that material the best amethyst is now referred to as "Siberian".
Now out of Nigeria has come an amethyst that I believe would at least meet and perhaps surp ass anything that came out of that period. My main supplier for raw African gemstones says that in forty years of buying and selling he's never seen it's equal. Deeply colored amethyst so very often has an inclusion (flaw) known as a veil. It is a layer of microscopic air bubbles. If there are too many of them, it lowers the value of the stone. The stones coming out of Nigeria are deep, mostly even color and appear to be entirely free of veils. A friend of mine thought that because of the deep color the stones had been heat treated but if Amethyst is heated it turns yellow. (There is amethyst from a deposit in Brazil which, if heated, will turn green and is then known as prasiolite). The Nigerian stones are so clean, that if it weren't for the natural crystal faces and terminations (points) one would take them for purple glass. I have cut one for a client and it is the most perfect amethyst I have seen. Beautiful dark, even color, clean and with the most dramatic color change from red purple to blue purple I have ever seen. She is had me build her a ring for it. I've also cut a large one for my wife, and pair of ovals for a man who'll be having earrings made for his wife. I am certain they'll be appreciated.
Happy Trails!