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What is the Rarest and Most Expensive Type of Obsidian?

The Rarest and Most Expensive Type of Obsidian

There are many types of obsidian out there, but some are much more valuable than others. One, in particular, is in a league of its own in both appearance and in expense. We’re going to take a closer look at that variety in this article.

So, let’s dig into the heart of the question!

So, Which Type of Obsidian Is It?

The variety obsidian that is the rarest and most valuable is called fire obsidian. This exceptionally rare form of obsidian displays rainbow colors when it’s displayed at the correct angle. These colors are usually quite bold and intense, but the obsidian retains a black appearance from most angles.

Fire Obsidian expensive and rare
Fire Obsidian (credit: Jessa and Mark Anderson/Flickr)

Previously, high-quality rainbow sheen obsidian was the priciest of the various varieties available but even the best didn’t demand anywhere near the price of fire obsidian. This optical phenomenon is comparable to labradorite but with more intense colors in many cases, in the best of cases they can compete with precious opal and other high-end stones.

This material is rare, coming primarily from one place in Oregon, as well as being hard to cut properly. Indeed, the rough of this stunning obsidian is often impossible to find at any price. Finished stones can often be found, as well as cabochons and the occasional specimen with a polished face to display the optical phenomenon.

Where Does Fire Obsidian’s Shimmer Come From?

Until recently, no one was quite sure what made the inside of fire obsidian light up like a neon rainbow. With some careful analysis, it’s been determined to be ultra-thin, large crystals of magnetite that formed internally.

This results in a unique effect in the world of stones. The optical effect of fire obsidian seems to be brought about by thin-film interference due to the ultra-thin magnetite crystals embedded in the obsidian.

Magnetite isn’t an uncommon inclusion in obsidian. In fact, magnetite is one of the two main minerals that give obsidian its deep, dark color. Along with hematite, it’s included in many samples of obsidian. But not every piece of obsidian contains the strange, ultra-thin crystals that make Fire Obsidian so unique.

The principle is the same as that of an oil slick on water. Due to the extremely thin crystal, we receive light reflected from both the top and the bottom of the same layer. The light then interacts with itself, creating the display of colors seen in things like Fire Obsidian or soap bubbles. It’s just a side effect when the layer of crystals is nearly as thin as the wavelength of visible light.

It’s a unique effect, especially since the black background of the obsidian makes the colors appear even more bright than they actually are.

Where is Fire Obsidian Found?

Oregon obsidian at glass butte
Glass Butte, Oregon

It appears that the only claims producing Fire Obsidian are from the area surrounding Glass Butte in Oregon. The exact location is where things get… complicated.

Mining claims are one of the more irritating things about collecting in public areas. The claims for obsidian in this area appear to have been grandfathered in, and recently the claims were switched from “obsidian” (which isn’t considered valid for claims) to “magnetite.”

The problem is that the law applies specifically to magnetite mined as ore, and it’s hard to argue that obsidian is a viable source of iron ore. This happened in roughly 2016, and I don’t believe it’s been challenged in court as of the time of this writing.

In other words: if you were hoping to go to a known location and find some fire obsidian for yourself… well, you’re probably out of luck unless you feel like dealing with a protracted court battle that will have a serious impact on rock collecting in the area.

That’s just a touch beyond our circle of expertise here. I’ll just advise you to be careful where you collect in the Glass Butte area if you’re not in the common public area.

There also appear to be locations where it can be found on the lands open to public access, but these locations are very closely guarded secrets. Fire obsidian’s rarity and extreme value (especially compared to other obsidian varieties)  make collecting this material in the wild much more complicated than a Google search and signing up for a message board or two.

This is compounded by the fact that not every piece of Fire Obsidian will be recognizable as such immediately. Fire Obsidian is usually found in small dykes near rhyolite. That’s about the best clue you’ll get unless you have a personal relationship with a local who knows the spots.

How Much is Fire Obsidian Worth?

The legal issues above are a complicated mess, and people are willing to stake a claim to the area in order to keep others out of their dig sites. The reason for all of that mess is simple: fire obsidian is the most expensive obsidian in the world… by far. 

A quick look at slabs shows that finding a pre-cut slab of the material for under $100 is nearly impossible. Cabochons start at $150 or more and just go up from there depending on the stone. Most “cabochons” made of the material are just polished flats due to the skill required in cutting Fire Obsidian properly.

Rough material (other than the ends of slabbed stones) is almost impossible to find. It wasn’t even possible to find an estimate of the “per pound” price for this stone.

In other words: Fire Obsidian is worth whatever someone will pay for it, and that’s often a lot.

This is a combination of rarity, lack of access, labor-intensive mining, and the fact that it requires an extremely skilled lapidary to make the most out of the material. Just getting a “wet” polish on obsidian is a task, try doing it while isolating a layer of magnetite that’s only a few millimeters thick.

By comparison, ultra high-grade obsidian cabs will usually run you less than $100 and the rough is usually around $12 per pound.

It’s definitely not hard to see why the locations are so rabidly protected at those kinds of prices. It’s also broken into the interest of fine jewelers, which will just make the price continue to go up.

Jeremy Hall
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