Recognizing Ruby and Sapphire in Nature

When you think of ruby and sapphire, you probably think of spectacular faceted gems in rings or in jewelry. Unfortunately, Mother Nature does not facet her gems: as a gem prospector, you need to learn the physical characteristics of this gemstone so you can identify the raw material in the field and know where to look in the environment. There are serious problems with most gemstone books - they are not designed for the prospector. Essentially all show spectacular faceted gems or museum quality specimens that you are unlikely to find in nature. So, here are some hints of where to look and what to look for.

 

The two photos above show the characteristic outline of corundum (the geologists term for ruby and sapphire). The upper photo is a cross-section of ruby in schist showing the characteristic hexagonal (6-sided) cross-section and the lower photo shows another corundum (pink sapphire) at an angle perpendicular to the upper photo. The mineral is still hexagonal, but now we are viewing the long axis which shows what geologists call a prism.

 

One of the few minerals that you might mistaken for ruby or sapphire is garnet. But don't feel bad as I've known geologists who make this mistake.

 

Ruby and sapphire also have atomic flaws known as parting where we can see these atomic planes in the crystals and these surfaces also provide locations for twinning of crystals. This are actual planes in the mineral that many gemmologists use to break the mineral, or avoid when they cut the mineral. These are useful in identifying the mineral because they do not occur in garnet. But few people are familiar with the term 'parting', so for our purpose, we will refer to these parting planes as "Cleavage", and corundum (sapphire and ruby) have three directions of parting ('cleavage').

 

Here is a very nice sapphire I found in Wyoming, but the gem cutter did a very poor job of avoiding flaws. For a geological researcher, this is a very nice specimen as it can be used to show cleavage and show others how one should not cut a gemstone. This cleavage is a plane of weakness and should have been avoided. The mineral should also have not been cut showing the dark mineral inclusions and it needed to be polished.

 

 

Another pink sapphire that I found that shows excellent rhombohedral cleavage in the gem. Note the two intersecting planes that are nearly perpendicular to one another.

 

Beautiful pink sapphire from Wyoming. The stone is flawed with numerous intersecting cleavage (parting) planes that can be partially hidden by cutting the stone in a cabochon.

Several rubies in a schist from the Wind River Mountains, Wyoming. Most prospectors would mis-identify these as rubies, but if you look close, you will see distinct, parallel cleavage in one of the rubies - something that does not occur in garnet.

This was likely the largest ruby ever found on earth! And it was found in Wyoming!  It exhibits excellent color but you are probably wondering what I'm talking about because you likely only see green zoisite with a little bit of ruby color. When this ruby formed, this entire specimen was one, very large, ruby. But it became unstable at deep in the earth's crust and reacted with metamorphic fluids until much of the ruby was replaced by the zoisite. Imagine wearing a ruby this size in a necklace. The base of the ruby was cut by a diamond-bladed rock saw.  Even though this ruby was flawed, it provides us with a general idea of what might be found in this particular deposit at depth. If this is ever mined, one likely will recover some very large rubies hidden beneath the surface.
 

Some corundum, such as this Oriental Amethyst (its not amethyst
but jewellers use this term for violet colored sapphires) will
produce twinned crystals attached to one another.

 

 

Here is a beautiful ruby that unfortunately is flawed with rhombohedral
cleavage. Even so, it makes a great gemstone. It is very rare to find a ruby
that is not flawed. Most are translucent like this one. I found this ruby south of
Encampment Wyoming.

 

Would you recognize these as rubies?  These rubies were found by my son Eric Hausel and they show nodular texture.

This photo shows a pink to violet sapphire prism to the left and a purple-red (pigeon's blood red) ruby in the rock to the right. The ruby is surrounded by what is known as a reaction rim of green zoisite.

In this photo, I'm holding rubies recovered from the Granite Mountains of Wyoming. Again, note that the rubies are enclosed by a reaction rim of green zoisite. This suggests that these rubies were all part of one large ruby at one time and part of the gem reacted with metamorphic fluids to produce the zoisite.
 

Another twinned Oriental Amethyst - you should be able to see that this corundum has two crystal that grew side by side.
 

 

Large, faceted red ruby from the Palmer Canyon ruby-sapphire-kyanite-iolite deposit in the Laramie Mountains. Note the distinct parallel cleavage planes.

 

Some of these gemstones will provide few hints of what they are. This 12-carat pink sapphire has an irregular shape, and is nearly flawless, But if you look closely, you will find at least one very distinct cleavage plane and also hints of rhombohedral cleavage


 

Wyoming's Ruby and Sapphire Deposits

Wyoming likely has some of the larger ruby deposits in North America. We found evidence for such deposits in a number of localities in the State, but ran into road blocks following every major discovery.

A 1.1 carat flawless ruby from Palmer Canyon

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RUBY & SAPPHIRE IN WYOMING

CORUNDUM (Al2O3)  Characteristics & Habit. Corundum (H=9) is the second hardest naturally occurring mineral: only diamond is harder. As a result, gemstones made from corundum are durable. Raw corundum occurs as barrel-shaped hexagonal prisms with rough, rounded surfaces often exhibiting distinct parting. Because of good rhombohedral and basal parting corundum prisms often terminate at basal pinicoids & display striations due to repeated twinning.

Corundum exhibits a variety of colors including gray, grayish green, blue, pink, brown, red & purple. Some corundum is used to produce extraordinary gemstones. Ruby is the deep pigeon’s-blood red translucent to transparent variety of corundum with adamantine luster and sapphire includes all other colors.

Hexagonal (6-sided) ruby in mica schist.

It will display a striking adamantine to vitreous luster noticeable in faceted gemstones. High specific gravity (4 to 4.1) is favorable for its concentration in black sand concentrates in streams. During sampling in the central Laramie Range, we recovered tiny rubies and sapphires in several sample concentrates in that region, suggesting that several corundum deposits remain to be discovered.

Palmer Canyon ruby mounted in necklace (photo courtesy of Chuck Mabarak) & showing cleavage (right - note the distinct lines in the gemstone).





THE CORUNDUM GEMSTONES include a variety of colors including:
Red Ruby
Cornflower Blue Sapphire
Colorless Leuco-sapphire
Light bluish-green Oriental Aquamarine
Green Oriental Emerald
Yellow-Green Oriental Chrysolite
Yellow Oriental Topaz
Aurora Red Oriental Hyacinth
Violet Oriental Amethyst

Occurrence. Corundum, a high-pressure aluminum oxide, is found with silica-poor aluminum-rich metamorphic rocks in areas of metapelite. Metapelite is the key to finding many gemstones in Colorado, Montana & Wyoming as discussed in my book (in preparation) The Geology of World Gemstone Deposits. Some discussions on these rocks are found in my new book on GEMSTONES in Wyoming.




Ruby with cleavage from
undisclosed location in WY

Metapelite may contain a variety of alumino-silicate porphyroblasts such as mica, kyanite, sillimanite, andalusite, vermiculite & cordierite. The corundum itself is typically found in vermiculite schist and aluminum-rich serpentinites. Vermiculite schist is considered an alteration product of a former metapelite in which metapelite was desilicated leaving mica-rich rock known as vermiculite schist or glimmerite schist. After noting the close association of vermiculite & ruby, I discovered several more ruby deposits in Wyoming. This was also true of iolite and pelitic schist. Using geology proved to be extremely valuable.

Twinned corundum with
distinct hexagonal cross-section

Small, twinned corundum from Wyoming. Note the 6-sided crystal prism that is bounded by pinacoids (flat surfaces).

Localities. Corundum has been found at a number of places in Wyoming. Wyoming could easily develop a major ruby and sapphire industry along with many other commodities - such as diamond, gold, palladium, rare earths, iolite, labradorite, copper, zinc and silver - but its political regime with the US Forest Service have worked for more than 30 years to withdraw nearly all non-energy mineral resources from public lands - something that should be considered illegal. Over the years, we provided evidence for major and world-class mineral deposits and several companies found significant base metal deposits, only to find government interference at every level.

One interesting locality lies northwest of Jeffrey City, known as the Red Dwarf deposit (sections 13 and 24, T30N, R93W), was investigated by me several years ago. The deposit consists of corundum gneiss & schist with a 5,000 foot strike length with widths of 20 to 50 feet. The rock has 1 to 10% corundum porphyroblasts encased in zoisite-fuchsite reaction rims and considerable fuchsite and zoisite pseudomorphs after corundum. Where found, some of corundum is translucent with good color.

Large ruby-zoisite porphyroblast collected at the Red Dwarf deposit by J. David Love of the US Geological Survey. Much of this giant ruby was replaced by zoisite, but some excellent pigeon’s blood red ruby remains untouched. Prior to replacement, this specimen would have been one of the largest rubies in the world. It also suggests that large rubies remain to be found at the Red Dwarf.

The corundum may be light purplish-pink, lavender, to reddish-purple, and range from millimeter size to more than two inches across. Some gem-quality corundum was found in the past and partially replaced specimens provide evidence for rubies of five inches (or more) in length and more than 2 inches in diameter.

A nearby serpentinite discovered west of the ruby schist contains tiny (millimeter size), light-blue, translucent to opaque corundum. Locally, the serpentinite has 20 to 40% corundum.

Ruby enclosed in reaction rim found by Eric Hausel at Red
Dwarf deposit in Granite Mountains.

At another deposit known as the Abernathy deposit (section 26, T30N, R96W) near Sweetwater Station, pale-blue and white corundum is found in mica schist. The corundum is abundant and occurs as one-inch diameter nodules in the schist.

Corundum is also associated with vermiculite schist (glimmerite) west of Wheatland in Palmer Canyon. This deposit (N/2 Section 18, T24N, R70W) is associated with kyanite, cordierite, and sillimanite schist and gneiss. The corundum forms small, hexagonal, pink, red and white grains from about 0.1 to 0.3 inch across. Many grains have well-developed parting which limits the size of facetable material. Even so, significant percentages have excellent color, and are transparent to translucent (Personal field notes, 1997). Locally, the schist may contain >20% corundum. Small amounts of corundum have also been identified at the Grizzly Creek iolite (cordierite) deposit to the south and other localities to the north.

Gem-quality 8 to 12 carat pink sapphire (left) & sapphire-kyanite schist from Palmer Canyon (right).




Some corundum was identified in vermiculite schist in the Platte River Valley between the Medicine Bow and Sierra Madre Mountains. Another notable corundum locality is in the Big Sandy opening along the southern margin of the Wind River Mountains, where hundreds of corundum crystals weighing up to 90 carats have been collected from Squaw Creek by prospectors (Russ and Joe Sims, personal communication). The source of this corundum remains undiscovered. Some nearby ruby schist float was found (B.F. Frost, Personal communication) suggesting that a potentially significant ruby deposit awaits discovery.

Photos of ruby, sapphire and iolite (blue) gems and raw material from Wyoming. Note the presence of parting (cleavage in some specimens - parallel fractures) and the 6-sided characteristic of the corundum.

Find more information about dozens of rubies and sapphire localities and methods I used to find several of these deposits from my book. See you on the outcrop - the GemHunter.


Below - Raw translucent pink sapphire from Palmer Canyon. Below right -  faceted pink sapphires & blue iolites from Palmer Canyon, & Below far right - large raw ruby from the Rattlesnake Hills, Wyoming. In addition to these stones, the author was following rubies near the Big Sandy opening in the Wind River Mountains, the Rattlesnake Hills, Barlow Gap, the Sierra Madre, the central Laramie Range & the Saratoga valley.