Recognizing Ruby and Sapphire in Nature

Low-quality corundum (variety - ruby) in a schist from the Wind River Mountains, Wyoming
(found by Dr. Ron Frost). Many prospectors would misidentify these as garnet, but look close, and
you will see distinct, parallel cleavage in the largest ruby - something that does not occur in garnet.

Best of Show - Rubies, sapphires, and iolite gemstones found in Wyoming and
faceted in Sri Lanka.

When you think of ruby and sapphire, you probably think of spectacular, faceted, over-priced gems in rings and necklaces. Unfortunately, mother nature does not facet gems: so a gem prospector must learn to recognize the natural, physical, characteristics of this gem to identify raw material in the field. And a prospector also needs to learn where to look in the field, and how to identify possible host rocks.

Some time ago, I received a 25-year longevity pin from the State of Wyoming for my service to the State. It was a tiny, plastic pin about the size of nickel that had a tiny, red, ruby. So, I took this spectacular gem to my lab to examine with a binocular microscope, and it was obvious that it was a synthetic ruby almost too tiny to weigh. The ruby may be worth about $1.00 and and the pin another $1.00 (pre-Biden prices). No idea where it was made, but my guess is China. If the state government had any creativity, one would think they would search for a good, Wyoming rock hound to dig some  Wyoming rubies (and other gems), facet them, and make them into longevity and dedication pins for their employees. As such, Wyoming would actually contribute to the state's economy and also provide a great means of advertising for the state's natural resources. Employees would be proud, particularly after they learned a little information about the history and gemology of the gems! 

When it comes to learning to identify minerals, there are flaws with most gemstone and mineralogy books - they are not designed for prospectors or rock hounds. Essentially, all books show spectacular, faceted, gems or museum-quality mineral specimens that are rare. 

Corundum in schist cut perpendicular to prism, showing 
distinct outline of hexagonal crystal habit. Sample from Wind
River Mountains collected by Dr. Ron Frost. Locality could
not be verified.

Hexagonal, prismatic corundum (pink sapphire) in vermiculite
schist, collected from Palmer Canyon, Wyoming. Yellow arrows
point to numerous crystals of pink corundum.

The two photos above show the characteristic crystal habit of corundum (geologists' term for ruby and sapphire). The upper photo shows a cross-section of ruby in schist with a characteristic hexagonal (6-sided) crystal habit, while the lower photo shows another corundum (pink sapphire) with its crystal habit perpendicular to crystal in the upper photo. This lower mineral is still hexagonal, but now we are viewing the long, crystal axis, which shows what geologists call a prism (or prismatic crystal habit). One mineral that is sometimes mistaken for ruby or sapphire, is garnet. But don't feel bad as I've known geologists who make that same mistake.

Ruby and sapphire exhibit atomic flaws known as crystal parting: linear, structural (atomic) planes in a crystal. This are actual planes in a mineral that gemologists might to break a mineral, or avoid when cutting the mineral, because they are a zone of weakness in the crystal. These are useful in identifying minerals like corundum (ruby, sapphire) and they do not appear in garnet. Few people are familiar with the term 'parting', but it is similar to mineral "cleavage". Corundum (sapphire and ruby) typically exhibits three directions of parting.

Pink sapphire from Palmer Canyon, Wyoming showing distinct plane cutting through the edge of
the gem. This is what is known as a parting plane. Most mineralogists describe corundum as having
three parting planes, while a few report the presence of at least one cleavage. However, cleavage
appears to be absent in corundum.

A 12-carat ruby collected in Palmer Canyon, Wyoming held by tweezer. Note the parallel lines
(twin planes) in the side of the crystal.

Beautiful pink sapphire from Wyoming. The stone is flawed by numerous intersecting (parting
planes.

Possibly, the largest ruby on earth (prior to alteration to the green zoisite! Yes, this was once all
 ruby, prior to changing physical conditions in the geological past that resulted in much of the
 former ruby being replaced by another mineral.  When the ruby formed, the entire specimen was
one, very-large, ruby. But it became unstable at depth in the earth's crust and reacted with
metamorphic fluids until much of the ruby was replaced by more stable zoisite. Imagine wearing a
ruby this size in necklace. The base of the ruby was cut by a diamond-bladed rock saw.  Even
 though the ruby was flawed, it provides us with a example of what may lie deeper at depth. 

This Oriental Amethyst (its not amethyst
but jewellers use this term for violet-colored
sapphires) will produce twinned crystals attached
to one another.

A beautiful ruby flawed with rhombohedral
parting. Even so, it makes a great gemstone. 
Most are translucent like this one recovered south of
Encampment Wyoming.

 These rubies were found by my son Eric Hausel and show nodular texture.

Pink to violet sapphire prism (left) with a purple-red (pigeon's blood red) ruby in rock
  (right). The ruby is enclosed by green zoisite reaction rim.

Ruby from Granite Mountains, Wyoming. Note the rubies are enclosed by green zoisite reaction rim. 
The zoisite reaction rim and ruby form a porphyroblast within the host rock - fuchsite schist.

Twinned Oriental Amethyst (oriental amethyst is an archaic term for lavender-colored corundum.

 

Pitted gem sapphire from Montana with rounded crystal faces.
This sapphire was collected from placer and the rounded crystal
faces are due to erosion and stream transportation.

Serpentinite with 15 to 20%, light-blue,  equigranular, sapphire discovered in the Granite Mountains
Wyoming by Robert Odell.

Sapphire schist from Palmer Canyon. Note the abundant white to very light blue hexagonal mineral grains. These are all sapphire and this particular sample has about 10% sapphire.

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.

RUBY & SAPPHIRE IN WYOMING

Faceted (transparent red) and cabochon (opaque cab) rubies sitting on specimen of corundum
vermiculite schist collected in Palmer Canyon (photo by the author. Gems weigh a little more
than 1-carat each.

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.

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 parting (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 often referred to as metapelite, mica schist and hornfels.



Ruby with parting 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.

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.

Large ruby-zoisite porphyroblast from Red Dwarf deposit found by J. David Love of the US Geological Survey. Much of this giant ruby was replaced by zoisite, but 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 suggests that large rubies remain to be found at the Red Dwarf.

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.

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. 

Beautiful specimen of reddish-purple corundum (variety - ruby) collected by Eric Hausel from the
Red Dwarf deposit, Granite Mountains, Wyoming (photo by Robert Odell).

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.

Palmer Canyon corundum schist showing some pink corundum (var. sapphire) enclosed within blue
kyanite in the vermiculite schist (photo by the author).

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.

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) indicating the presence of ruby deposit. According to Dr. Frost, this ruby deposit is widespread within the southern core of the Wind River Mountains. Location, however, could not be verified and may be erroneous.

 

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.