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Amethysts and Arizona


The mountain is called Four Peaks. I can’t quite see it from my house because Superstition Mountain rises between us, but a walk or drive of less than a mile brings Four Peaks into view. Though it’s rarely covered with snow, this truly purple mountain majesty is readily seen all over Arizona, and in fact anywhere an Arizona vehicle drives. Four Peaks is featured, appropriately in purple, on our Arizona license plates.


The sunset on the mountains isn’t the only reason for the colorful description. Four Peaks is the location of one of the world’s most famous amethyst mines, and the only commercial amethyst mine in the United States.

Amethyst used to be considered a precious stone, along with diamond, emerald, ruby, and sapphire. Those latter four continue to be precious because gem-quality material remains relatively rare. Amethyst lost its “precious” distinction when huge deposits were discovered in Brazil (see sample below) and other parts of South America in the 18th century. Amethyst’s loss is our gain, because abundant supplies means lower costs!


Diamonds are carbon crystals. Rubies and sapphires are corundum; emeralds are beryl. Amethysts are silicon dioxide, or just another variety of one of the most abundant minerals on earth, namely our old friend quartz. It’s not really surprising then that amethysts show up in many localities around the world, and especially in Arizona.

Several years ago, my late husband and I were rock hunting at a location where we had previously found some purple jasper and some crystal-lined geode fragments. Putting the two together, I thought it quite possible that we might find some amethysts. Maybe not gem quality crystals, but who knows? When I spied a baseball-sized chunk of rather nondescript rock that looked like it might have a vein of agate running through it, I asked for the rock hammer.

“I wanna whack this rock,” I said.


He laughed. “You think you’re gonna find amethysts?”

With a confident grin, I replied, “No, I don’t think so. I know so.”


They’re very pale lavender and they’re cloudy rather than clear, but they were really amethysts! How did I know they were there? To this day, I can’t tell you. But I just knew. Later we found a few more similar light-colored crystals in the same area, but never anything like Four Peaks!

A few years ago, I acquired some raw Four Peaks crystals from an elderly friend who had collected them himself 40 or 50 years ago. Photographs can’t do them justice.

Four Peaks 005b

Four Peaks 007

Because amethysts get their lovely purple color from traces of iron that mix with the silicon dioxide of quartz, some of the crystals from Four Peaks are coated with hematite, an iron oxide, in the form of a shiny, sparkling reddish-brown crust.

Four Peaks 010b

To fully appreciate these gems in the rough, you have to put them in perspective.  How big are they?  They can be pretty darn big!


One of the characteristics of Four Peaks amethysts is that they often have a red flash.  This means that when faceted, the finished gem will show a spark of bright red when moved to catch the light.  I make no claims to be a great photographer, but I did catch just a tiny bit of the red flash in this little rectangular cut Four Peaks amethyst, photographed in bright early morning sunshine.





Not all of Arizona’s amethysts form nice big distinct crystals like the jewels of Four Peaks.  A few months ago I purchased a slice of amethyst and citrine that came from a mine in western Arizona.  Here the individual crystals are smaller and mingle in a more massive formation.  Citrine and amethyst often occur together, and when in the same crystal they are called ametrine.  In this cabochon you can see the crystals in the formation, both purple and yellow-orange.


Held up to the light — in this case, the rising sun — the color variation is even more dramatic.



Because the amount of iron varied as the silicon dioxide crystals formed, amethysts range in intensity of color from the pale lavender of my whacked stone to the deep purple of that little rectangular faceted stone.  And as you can see in the photos above, an individual crystal may fade from the very dark purple at the termination point down to almost white at the base.  Here’s a nice sized — but imperfectly cut — round amethyst that exhibits a not uncommon streaking of the color.  That’s a good indication this is a genuine amethyst and not a fake.  Fakes — usually glass or a vibrantly colored cubic zirconium — tend to be uniform in color and flawless.  This stone not only is streaked with darker and lighter bands of purple, but it also has inclusions and other flaws that are rarely present in lab-created gems.



Arizona has several other purple gemstones besides amethyst.  The Burro Creek and Sheep Crossing rock collecting areas produce lovely purple agates.  Though I haven’t been to Burro Creek — yet! — I’ve been to the Sheep Crossing and it’s everything the guidebooks say . . . and more!  Maybe next blog post we’ll go there.



All photos copyright Linda Ann Wheeler Hilton