casitas de gila guesthouses bed and breakfast new mexico 575-535-4455
info@casitasdegila.com

Southwestern Guesthouses on 265 Acres
near Silver City, New Mexico
overlooking Bear Creek and the Gila Wilderness

Casitas de Gila Nature Blog

Casitas de Gila Nature Blog

WILDLIFE !

Another of Becky’s contributions to Michael’s Nature Blog …

 

We didn’t have a lot of rain this summer — only about 6 inches so far this year — but there is water in Bear Creek, below Casitas de Gila Guesthouses, and that water is drawing in the wildlife.

Our neighbors and friends Bill and Dale have a game camera and are always delighted to share their “captures” with us and with our Casita guests. Presently the camera is set up in a dry wash near Bear Creek, and it seems to be a pretty good spot.

We know there are COATIMUNDI around. They are a very shy animal, so all we have ever managed to see is a tail hanging down below a tree branch. But this fella was drawn to the salt block and water bowl …

coatimundi

 

And so was another shy animal a few days later … a BOBCAT! We see their scat and often hear them calling at night, so we know they are always around, but we have only actually seen one a couple of times. This fella was also drawn to the salt block and water bowl …

bobcat

 

A few weeks ago, while chatting with some guests in the afternoon outside Casita del Sol y la Luna, out of the corner of my eye I caught a glimpse of some quail. We have lots of Gambel Quail here. Cute little birds with a wonderful plume on their heads. But my jaw dropped when I realized that these four little birds, with their distinctive markings, were Montezuma Quail! Described as “secretive”, these little birds quickly made their way down the cliff below the Casitas while I watched in absolute wonder. Seeing these elusive birds was the wildlife highlight of my 14 years in Gila, New Mexico. I have been watching for them ever since, but alas, haven’t seen them again. And no, I have no photo. Unlike many of our guests, I usually do not have a camera with me. But I did carry one around for a while! And I am still looking …
 

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Fall Color in Southwest New Mexico

 
IN OCTOBER BEAR CREEK BECOMES A RIVER OF GOLD

fall color in southwest new mexico

Late October and early November are a gorgeous time here at Casitas de Gila Guesthouses in Southwest New Mexico. With cool nights reaching down to near-frosty levels and daytime temperatures bouncing up into the high 70s or low 80s, the leaves on the cottonwoods, sycamores, willows, and ash reach their peak colors during this annual two- to three-week passage into Fall. In addition to the effects of the wide temperature swings, the brilliance and saturation of color in the canyon varies from year to year, depending upon the amount of Summer rain. Too little and the colors are washed out and pale; too much and the leaves just turn shades of brown. But when the temperature swings and rainfall amounts are just right … well, looking down on Bear Creek canyon from the Casitas above is a marvelous sight to behold. Indeed, it is a river of gold. And so it is this year!

No matter what time of day, or wherever you are at the Casitas, the golden glow emanating from Bear Creek canyon demands your attention and envelops you. Emerging from your Casita in the morning, the canyon’s radiating warmth draws the eye and embraces one’s Soul …

View from Casitas de los Arboles

View from Casita de los Arboles

View from Casita de los Pajaros

View from Casita de los Pajaros

View from Casita de Sol y la Luna

View from Casita del Sol y la Luna

View from Casita de las Flores

View from Casita de las Flores

View from Casita de los Animalitos

View from Casita de los Animalitos

View from the Hot Tub

View from the hot tub


fall color near Silver City, New Mexico

O come! the radiant Colors entreat … O come! and along the trails we’ll meet!

Just make your way north down the hillside trail …

Or maybe head south, where the high cliffs prevail …


fall color along Bear Creek in New Mexico

Passing quietly along the floodplain path, the brilliant sun filters down through still-shaded corridors, creating a complex mosaic of light and shadow …

fall color in southwest New Mexico

To suddenly give way to a clearing of gold and orange brilliance …

Continuing on, it is almost as if the falling leaves are once again speaking out in a faint but enticing way …

Along the Creek you’ll find special places, where silence reigns and Nature’s beauty graces.

fall color near Silver City, New Mexico

And amongst the fallen leaves a hammock is found waiting. One cannot resist the temptation to pause, lay back, and watch the leaves fluttering down from the ancient cottonwood above, like so many giant golden snowflakes …

full moon in southwest new mexico

Of course, not everyone is an early riser … Or if, perchance, you are one of those who has stayed up most of the night tracing the arc of a golden Harvest Moon across the dark and crystalline sky, then the golden leaves will be still be there for your personal afternoon delight later in the day …

fall on Bear Creek at Casitas de Gila Guesthouses

Not to worry, dear weary guest; just sleep away the morning gold in bed, and catch the afternoon show instead! For, indeed, as some connoisseurs of bright leaf attest, it is then when light and shadow are at their exquisite best! …

The Creek’s still waiting down below, your morning’s absence it didn’t mind …
And while much afternoon brilliance still remains …

fall color along bear creek

The shadows deeper now you’ll find …

The hammock, too, waits for you still …
Until once again you must climb up that hill …

October Bear Creek Gold 2012

brilliant fall cottonwoods in southwest new mexico

 

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SAN FRANCISCO HOT SPRINGS

 
A Day Hike to the San Francisco Hot Springs and the Pristine Wilderness of the San Francisco River Canyon

San Francisco River Canyon New Mexico

Looking west down into the San Francisco Canyon where the floodplain narrows and the river enters deeply-incised meanders

The San Francisco River is the largest tributary to the Gila River. Over its 160-mile course, it flows through some of the most scenic country in Southeastern Arizona and Southwestern New Mexico. Emerging from its mountainous headwaters near Alpine, Arizona, in eastern Apache County, the San Francisco flows eastward into New Mexico’s Catron County before looping south and then westward back into Arizona, where it joins the Gila River a few miles downstream from the historic town of Clifton in Greenlee County. Along its course, the San Francisco flows through diverse landscapes, alternating between sparsely settled, broad, open valleys, ranched and farmed since the pioneer days of the late 1800s; and narrow, rugged, deeply-incised canyons of pristine wilderness, once the familiar and well traveled thoroughfare of a hundred or more generations of Native Americans, but rarely visited today.

For much of its course through New Mexico, the San Francisco River flows through Gila National Forest land where various forest roads and trails provide public access points to the river within a rugged, mountainous terrain. But it is the last 15 miles of its New Mexican sojourn, just before reentering Arizona, where the San Francisco travels the most remote, isolated, and inaccessible segment of its journey. It is along this stretch of river that the San Francisco descends into a wild and pristine canyon comprised of an increasingly narrower and deeper series of tightly looped, entrenched meanders as it traverses an uplifted complex landscape of Miocene and Oligocene layered volcanic deposits over a thousand feet in thickness and some 18-26 million years old1.

It is at the upstream entrance to this deeply entrenched and narrow canyon that the San Francisco Hot Springs Trail is located.
 

THE SAN FRANCISCO HOT SPRINGS

San Francisco Hot Springs New Mexico

US Forest Service kiosk at the trailhead to San Francisco Hot Springs

Of the numerous hot springs that occur throughout the Gila National Forest, the San Francisco Hot Springs group is one of the better known and more easily visited. The springs are located about 8 miles south of Glenwood, New Mexico (about 35 minutes northwest of Casitas de Gila Guesthouses). They are readily accessed from a half-mile long, county-maintained gravel road leading from US Route 180 to the trailhead for the San Francisco Hot Springs Trail. The trail to the hot springs is a 1.5-mile moderately-difficult hiking trail leading down into the magnificent San Francisco River Canyon where the springs are located.

The San Francisco Hot Springs consist of three separate groups of springs that are spread out along a quarter-mile of the river floodplain. The Upper Group of hot springs occur on private property, just north of the Gila National Forest boundary, and provide water to the privately-owned Sundial Springs. The Middle and Lower Group of springs are on Gila National Forest land immediately downstream from the Upper Group, and are accessible from the San Francisco Hot Springs Trail. Temperature of the springs is reported to range from 100 to 120°F depending upon the stage of river flow2.

The Middle Group of hot springs, sometimes referred to as “The Bubbles”, occurs against a rock cliff on the west side of the river, directly across from where the San Francisco Hot Spring Trail comes down to the river.

The Lower Group of hot springs occurs about 450 feet south of the Middle Group and is also located on the opposite side of the river, right where the canyon and river make a sharp turn to the west.

Like many of the hot springs found in the Gila National Forest, the San Francisco Hot Springs are located within the floodplain, at the bottom of a canyon, and are associated with a major fault, which in this case is the NNW trending Sundial Mountain Fault1, which crosses the San Francisco River canyon right at the Lower Hot Springs. The Sundial Mountain Fault is a high-angle dip-slip normal fault, dipping NE between 60 and 80°, and most probably serves as the conduit for the hot waters ascending from deep within the earth.

Because the San Francisco Hot Springs are located within the floodplain of the river, with several being right at the river’s edge, the exact location, size, and even the actual presence of the various springs will vary from year to year depending upon the number and magnitude of flood events on the river. During consecutive years of few or less-intense flood events, visitors to the springs will typically construct rock-lined pools around the emanating hot springs, which will serve as sitting pools until the next flood wipes them away, and the construction of new pools commences. However during the more severe flood events, it is often the case that the river channel will experience significant lateral movement, sometimes moving completely from one side of the canyon to the other. During these times, returning visitors may find that their favorite hot springs have been buried completely by the migrating river deposits, and then discover that new springs have emerged nearby.

It seems important to conclude this overview on the nature of the San Francisco Hot Springs by stating that a trip to the San Francisco Hot Springs is almost always a great hike even if the Springs themselves are not at their best for the reasons stated above. The scenery is gorgeous, the rugged and pristine San Francisco River Canyon downstream from the Springs is spectacular, intriguing, and challenging, and the bird and animal populations abundant and diverse. High water during the spring runoff (February through April), or the summer monsoon season (July through mid/late September) will sometimes limit trail access and prohibit river crossings, but during other months of the year it is not generally a problem for those interested in a longer hike down the river. For those looking for a short, easy to moderate, yet highly interesting hike through a diverse and unique landscape, a visit to the San Francisco Hot Springs area is highly recommended.
 

AN “INTERESTING” HIKE TO THE SAN FRANCISCO HOT SPRINGS

San Francisco River Canyon New Mexico

Looking northwest at the top of the San Francisco Canyon where the trail begins its steep descent to the river below

And thus it was, one late August day last month, that my good friend Bill Marcy and I decided to spend some time hiking and exploring in the San Francisco Hot Springs area and to check on the status of where the springs might be now. Bill had been there before, but I had not, despite having known of them and been told numerous times about how interesting the area is. While I am not a hot springs soaking enthusiast, as a geologist I find them fascinating and over the years have developed a strong interest in the geology and hydrology of their occurrence.

Now August, of course, is generally the peak of Southwest New Mexico’s Monsoon Season, but we weren’t at all concerned since the summer monsoon showers and thunderstorms, while they can be intense at times, generally don’t last more than half an hour before the sun comes out again to dry everything. Plus, according to the National Weather Service, the probability of rain for that day was only 40%. And so, without further thought, I packed my gear and lunch, drove over to Bill’s, where we loaded our two dogs, Big Red and Bower, into Bill’s truck and headed out.

A morning’s drive up US 180 towards Glenwood is always a gorgeous trip, with the ancient Burro Mountains rising to the south and the vast ramparts of the towering Mogollon Mountains of the Gila Wilderness to the north, glistening and beckoning in the morning sun. This morning was no different. At least it started out that way. However, after about a half hour’s journey, we noticed that the Mogollons were no longer glistening. In fact they were actually looking rather dark and foreboding, their higher peaks shrouded in rain clouds. Looking ahead towards the mountains surrounding our destination, the sky seemed to be even darker. But, no matter, the mountains and the open trail were calling and we were on our way!

Arriving at the San Francisco Hot Spring trailhead, we both noticed that the dark clouds were indeed now quite a bit darker, borderline black maybe, and seemed to have taken on a sort of roiling motion as well. But the call of the open trail was even louder now, so we hoisted our packs and headed out.
 

THE SAN FRANCISCO HOT SPRINGS TRAIL

San Francisco Hot Springs Trail

The trail leading to the San Francisco River Canyon

The first mile of the San Francisco Hot Springs trail follows a gently downhill sloping grass-covered arroyo, dotted with numerous Alligator Juniper (Juniperus deppeana), Piñon Pine (Pinus edulis), Honey Mesquite (Prosipus glandulosa), and Desert Scrub Oak (Quercus turbinella) trees. The trail itself is impossible to miss, having been worn down as much as a foot into a clayey, pebble-to-boulder strewn soil by numerous hikers, cows, wildlife, and rainwater runoff over the years. As the hike progressed, we noticed with some interest that clay minerals, not all that common over most trails in our area, here seemed to be the major constituent of the trail we were walking on. Once aware of this fact, we then noticed how much of the ground and trail surface showed extensive shrinkage cracks dried out by the summer sun. “Hmmm,” murmured the scientific voice quietly within, “bet this trail gets really sticky during a hard rain!”

At about the one-mile mark the edge of the San Francisco River Canyon is reached, marked by a barbed wire stock fence with a convenient off-set stile provided for the trail to pass through. Once past the fence, the trail begins a steep, quarter-mile descent of about 200 vertical feet to the bottom of the canyon. Here, the loose clayey soil of the previous mile disappears and the trail switchbacks down a rock surface composed of hard, angular to sub-rounded cobbles and boulders of mostly dark gray volcanic andesite, which are set in a softer, fine-grained, light-colored matrix. It is an unusual rock type, and one that once exposed to weathering, produces a very rough and lumpy surface, not slippery at all, but providing excellent traction. Yet because of the way the encased cobbles and boulders protrude from the softer matrix, we quickly noticed that it can also be a somewhat treacherous surface that is easy to trip on, especially when one gets too engrossed in the magnificent view of the sheer, volcanic cliffs now lining the canyon ahead and below!

We were about halfway down this lumpy section of the trail when the first rain drops began to fall. It was also at this point that Big Red and Bower sensed the presence of the San Francisco River another 100 feet below. Water! How nice! … Our favorite thing! … Let’s go jump in! And off they went at a run, down the steep slope with their owners struggling to keep up, having just noticed with more than a little consternation that the river seemed to be running a bit high and swift.

We arrived at the river’s edge just as Bower charged in, only to discover that his point of entry is at a cut-bank of the river and he is immediately over his head. Sensing danger in the depth and strength of the current, Bower responded immediately to my frantic call, swam back, and climbed out. Big Red, the more mature and thoughtful red-bone hound that he is, had halted at the water’s edge, and watched all knowingly as his impetuous younger friend dragged himself up out of the dark swirling water and shook off. It is then we noticed that my normally white-and-brown Springer Spaniel has taken on the appearance of a very slimy, dark-chocolate-brown labrador retriever! The cause of the dark color of the water is immediately obvious. The effects of the Whitewater-Baldy fire (May-June 2012) within the Gila Wilderness were still making their way downstream … the normally crystal clear and lively waters of the San Francisco River were now a swirling, heavy, viscous torrent of very dark chocolate.

The first drops of rain had multiplied exponentially and it was now raining hard. We stood at the water’s edge where Bower had taken his brief swim and could see the Forest Service trail marker leading to the Middle Group of hot springs beckoning on the other side. But not today. The river was running very swiftly, and because we were unable to see the bottom (because of the suspended ash and soot), it was impossible to tell how deep it was. “Don’t even think about it”, advised the soft voice within.

Rain!

Waiting out the downpour in the Arroyo of Little Relief. (The blurriness of this photo is not a focusing or movement problem . . . it’s because of the amount of rain cascading down upon man and beasts!)

The rain had just turned from hard to harder. To the left of where we stood another Forest Service trail marker pointed south, down-stream through a mature riverine forest, towards the imposing cliffs we had seen during our descent into the canyon. This trail, we knew, would lead to a point where under normal water level conditions the trail would once again cross the river to the Lower Group of hot springs. Visiting those hot springs would have to wait for another day, but we hurried down the trail anyway towards the towering old growth cottonwoods (Populus fremontii) where we hoped to find some shelter from the approaching center of the thunderstorm cell, which by the telltale increasing frequency and decibel level of the thunder, would soon be upon us.

Anyone who has spent much time in the Southwest knows all too well the dangers of seeking shelter from a storm under old cottonwoods, particularly in the summer when they are in full foliage and their branches are heavy with water. Even in a moderate breeze on a fine sunny day their weak and brittle limbs can suddenly break off and fall to the ground, crushing anything below. But this was not a breeze; this was turning in a maelstrom of hurricane-force wind and rain. So we hurried by several big cottonwoods, taking notice of a one-foot diameter specimen freshly felled by some champion of the local beaver (Castor canadensis) population and an even more impressive and still standing, 16-inch diameter cottonwood that had been chewed all the way through except for a thin, 2-inch thick portion on one side. Now there was a real beaver trap … craftily set for unsuspecting humans!

San Francisco Hot Springs New Mexico

The spectacular cliff where we should have waited out the storm

Just as the rain turned from harder to hardest, the trail passed by a small, narrow, and steep-sided arroyo with a gnarled Desert Scrub Oak (Quercus turbinella) spreading a thick canopy of non-lethal little branches that partly shielded the slightly undercut north side of the gravel bank of the arroyo. Thinking we could do no better, we decided to hunker down here to wait out the storm. No sooner was the decision made and we started to take off our packs when a lightening bolt struck the rocky slope of the canyon wall above us, less than a hundred feet away, with a simultaneous, resounding crack of thunder that made all four of us jump while simultaneously eliciting various yells, howls, and whimpers. The center of the storm had arrived. And along with it came an immediate change in wind direction and a crescendo of pounding rain that converted our once seemingly-protected spot into something akin to being trapped at the bottom of a giant waterfall.

But just as we felt we were going under for the third time, it was over. In a few minutes, the clouds began to brighten and it seemed that the sun was considering an appearance. Encouraged, we decided to follow the trail a little further. Soaked and chilled to the bone by the now 20 degree cooler temperature, the thought of moving was inviting.

San Francisco Hot Springs New Mexico

Negotiating the ledge at the water’s edge

Just past the mouth of our small arroyo-of-little-relief, we were immediately confronted with a 50-foot section where the the trail suddenly disappeared, submerged by the swollen river that was now running hard up against a steep bank of very loosely consolidated, slippery, fine-grained silty material that was slowly eroding into the creek. After some serious cogitation of the situation, we convinced ourselves that the one-foot-wide rocky ledge that was slightly awash at creek level should enable us to make our way safely across. It did. Once on the other side, the trail re-emerged to once again enter a widened floodplain, substantially vegetated with mature cottonwoods and other trees. A short distance into this forested floodplain, the trail leads to an impressive and visually-striking vertical cliff of horizontal beds comprised of two very different and distinctive rock types. The lower 10 to 13 feet of the cliff consists of loosely consolidated fine-grained material, similar to what we had just passed over at the water’s edge, which has been eroded and weathered back at least a good 5 to 10 feet beneath an imposing overhanging layer of undetermined thickness composed of angular to sub-rounded, dark-colored cobbles and boulders of mostly andesite, set in a light tan, fine-grained matrix, very similar to what we had passed over on the steep portion of the trail on our descent into the canyon. Here was were we should have waited out the storm!

The skies had once again turned black and with the sound of thunder we knew another storm was approaching from the south-southwest. It was time to turn around and head back.The threat of another soaking was not the problem. The real concern was that the storms in the area seemed to be intensifying as the afternoon wore on and were tracking right over the western end of the highest section of the Mogollon Mountains, upstream and to the north of us, where the duration and amount of rainfall we knew would typically be greater and would soon be draining directly into the San Francisco River upstream from us. The likelihood of a flash flood was increasing by the minute, and because we were now downstream from the difficult spot we had just crossed at water’s edge, even a two- to three-foot rise in river level could prove to be very problematic. Knowing that having reached the spectacular cliff in front of us, we were now no more than a quarter-mile from entering the deeply entrenched, cliff-lined meanders of the San Francisco River, it was really tempting to continue. But it would have to wait for another day. Once more the little voice within was speaking out, “No! It’s time to go! Get the heck out of here!”

Examination of Ratte and Brooks’ 1989 geologic map of the San Francisco Hot Springs area1 shows that all of the San Francisco Hot Springs trail we had just traversed, from the trailhead to our turn-around point at the spectacular vertical cliff described above, is mapped as a locally derived, over-600-foot-thick fanglomerate deposit within the Gila Conglomerate Formation of Pleistocene to Miocene age, which occurs on the east, down-dropped side of the Sundial Mountain Fault described earlier. Had we continued our hike just a few hundred feet to the west of our turn-around point, we would have crossed the Sundial Mountain Fault and passed into the layered volcanic deposits of the Upper Andesite member of the Bearwallow Formation. This Upper Andesite Member, which has been dated at being 24.7 million years old, is the source of the fanglomerate deposit on the east side of the fault. The fanglomerate deposit was formed when the Upper Andesite deposits were being uplifted and eroded on the west side of the intermittently active Sundial Mountain Fault, and the eroded material was then being transported by streams to the east across the fault, where it was quickly deposited as coalescing alluvial fans in a rapidly subsiding down-dropped elongated basin or graben, between the northern Burro Mountains on the West and the Mogollon Mountains on the east. In the geological literature this basin is known as the Mangas Trench, and is one of several NW trending basins in the surrounding region of New Mexico and Arizona. Based on dating of various basalt deposits within these basins, the faulting along the margins of these down-dropped basins began shortly after 19 million years ago, and persisted intermittently for millions of years, allowing thick deposition of alluvial sedimentary deposits consisting mostly of conglomerates, fanglomerates, and sandstones derived from the uplifted surrounding mountains3.

San Francisco Hot Springs Trail New Mexico

An army of lichen-covered andesite boulders captured in their inexorable creep through time and space down the northeast slope of Sundial Mountain

The initial part of the trip back out of the canyon went quickly as the next storm progressed slowly towards us. However once the top of the canyon was reached, our pace of travel slowed considerably as the trail wound its way uphill, across the mile of cobbles and boulders embedded in the heavy, clay-rich soil. The once firm, mud-cracked ground surface commented on during our hike in was not so firm anymore, and once again the little voice had been right. The going had now rapidly progressed from sticky to stickier, and finally to extremely sticky … And with every step, the size and weight of our cleated boots became larger and heavier, reminiscent of one of those dreams where no matter how hard you try, your feet and legs will hardly move and you can’t seem to get away or make any progress.

Eventually the homeward slog ended and we reached the trailhead, where several pounds of sticky clay was scraped off. After a short but most welcomed and enjoyable lunch, we loaded up the dogs and headed for home, just as the first drops of rain from the arriving thunderstorm began to splatter on the windshield. Indeed, it had been an “interesting” day.

San Francisco Hot Springs Trail New Mexico

The trail through clay and boulders starting to get sticky

     
San Francisco Hot Springs New Mexico

A top contender for the Best in the West “Outhouse with a View” Award, here looking north towards the magnificent Mogollon Mountains


DIRECTIONS TO THE SAN FRANCISCO HOT SPRINGS

The San Francisco Hot Springs trailhead is located at the end of a one-half-mile long, county maintained, all weather, gravel access road that leaves US Route 180 around Mile Marker 58, a point 6.5 miles south of the road entrance to the Glenwood District Ranger Station and 5 miles north of the turnoff on US 180 for the Leopold Vista Overlook rest area. GPS coordinates for the access road turnoff leading to the trailhead are N33°14.025′, W108°51.651′. A newly-constructed restroom building is available at the trailhead, but water is not.


REFERENCES

1. Ratte, J.C. and Brooks, W.E., 1989, Geologic Map of the Wilson Mountain Quadrangle, Catron and Grant Counties, New Mexico: U.S. Geological Survey, Geologic Quadrangle Map GQ-1611.d

2. Bischoff, Matt C., 2008, Touring New Mexico Hot Springs, 2nd edition

3. Houser, B.B., 1994, Geology of the Late Cenozoic Alma Basin, New Mexico and Arizona, New Mexico Geological Society Guidebook (download .pdf file), 45th Field Conference, Mogollon Slope, West-Central New Mexico and East-Central Arizona
 

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OBSIDIAN

Forged by Fire • Treasured Through the Ages
 

obsidian rocks

Typical shapes of Mule Creek Marekanites; size range averages 1 to 5 cm, although some may go as large as 10 cm.

Among the wide range of volcanic rocks and minerals that can be found near Casitas de Gila Guesthouses, one of the most interesting is obsidian. In geologic terms, obsidian is classified as an extrusive igneous rock or sometimes a mineraloid, but never as a mineral because it does not have a crystalline structure. Instead it is a naturally-occurring amorphous volcanic rhyolitic glass, formed when a magma or lava flow, highly rich in SiO2 cools so rapidly that crystalline minerals do not have time to form. Typically, obsidian contains between 70 and 75% SiO2, substantial amounts of magnesium oxide (MgO) and iron oxide (Fe3O4), plus numerous trace elements, such as rubidium (Rb), cesium (Cs), strontium (Sr), barium (Ba), lanthanum (La), cerium (Ce), yttrium (Y), titanium (Ti), zirconium (Zr), phosporous (P), tantalum (Ta) or niobium (Nb).

Obsidian is easily identified by its glassy, conchoidal fracture and its brown or smoky-gray to black color. Sometimes it may contain inclusions of small, white crystals of the mineral cristobalite, a high-temperature form of SiO2, or it may contain linear or swirling patterns of extremely small gas bubbles retained within the flowing magma or lava before it was rapidly cooled.

perlite

Perlite showing bedding layers and swirling texture

Obsidian is found around the world wherever rhyolitic magma (containing 70% or more SiO2 and less than 2% water) occur. In the United States, obsidian occurs in most western states and is abundant within western New Mexico and Arizona. Similar deposits of obsidian occur just south of the border in the Mexican States of Sonora and Chihuahua.

Obsidian is not stable at the earth’s surface and consequently is rarely found in rocks more than a few tens of millions of years old. The reason for this is that over time, ever so slowly, obsidian absorbs water into its structure, and once that happens the obsidian converts to another natural glass or mineraloid called perlite. Thus, many volcanic deposits that originally formed as obsidian are now entirely converted to perlite. Not all perlite deposits form from hydration of obsidian, however. If a rapidly cooled, rhyolitic magma contains 2% or more water to start with, then the resultant volcanic glass will solidify as perlite, not obsidian.
 

THE MULE CREEK REGION OBSIDIAN DEPOSITS

mule creek, new mexico

Mule Creek Country. Outcrop of rhyolitic ash flow deposit in foreground.

The geologic history of western New Mexico during the Late Paleogene to Early Neogene Periods (old terminology Mid to Late Tertiary) was basically a time of extensive and ongoing volcanic activity. By the end of Oligocene Epoch the lengthy period of massive eruptions of the Super-volcanoes within the Gila Wilderness (35-28 million years ago) had come to an end, and the focus for most of the ensuing volcanic activity within the Grant County/Catron County, NM, border area over the next 10 million years or so during the Miocene Epoch shifted westward towards the Arizona/New Mexico border and into eastern Arizona. It was during this time between 20 and 17 million years ago that the obsidian deposits of the Mule Creek region were formed.

obsidian

Broken Marekanites displaying conchoidal fracture

Extensive research by M. Steven Shackley, Department of Anthropology at the University of California at Berkley, regarding archaeological sources and use of obsidian in the American Southwest indicates that the Mule Creek Obsidian Deposits are probably the most extensive occurrence geographically of obsidian anywhere in the Southwest. The deposits are located about 20 miles northwest of the Casitas and occur within a greater than 100 square mile area that centers around the small community of Mule Creek, New Mexico, about five miles from the Arizona border. Within this vast area that includes portions of Grant and Catron Counties in New Mexico and Greenlee County in Arizona, are numerous, extensive obsidian-bearing volcanic rhyolitic ash flow deposits. When found in place, the obsidian occurs as small nodules, generally two inches (5cm) or less in diameter, but occasionally up to twice that size, within outcrops of perlitic ash-flow deposits that absolute dating shows were ejected 17.7 million years ago.

marekanites in perlite matrix

Close-up of Marekanites in Perlite matrix layer within Mule Creek rhyolitic ash flow deposit

The scientific name for these obsidian nodules is marekanites which take their name from the Marekanka River in the Okhotsk basin in Siberia, Russia, where they were described over a hundred years ago. A more recent, common name that is often given to these obsidian nodules is that of “Apache tears”, a name coined by mineral collectors, rockhounds and lapidary enthusiasts for the obsidian nodules found in the American Southwest. In addition to the widely distributed outcrops of marekanite bearing perlite deposits of the Mule Creek Obsidian Deposits, the obsidian nodules also occur as a significant constituent of virtually all Quaternary Period alluvium deposits which have been eroded from the bedrock outcrops and redeposited in stream beds and valleys throughout the region.
 

TREASURED THROUGHOUT THE AGES

Perlite layer

Perlite layer within Mule Creek rhyolitic ash flow

Obsidian has been a treasured natural resource of prehistoric and historic cultures worldwide since the beginning of the Stone Age because of its glassy composition and conchoidal fracture, allowing the rock to be easily worked into extremely sharp projectile points, cutting blades and other tools. Because of its limited occurrence, good sources were highly sought after by prehistoric cultures, most likely fought over, and became the basis of early production centers, commerce, and trade routes.

Archaeological research of the late pre-historic cultures of the American Southwest and Northern Mexico conducted by Dr. Shackley at the University of California at Berkley and research done as part of the Preservation Fellowship Program at the private non-profit organization Archaeology Southwest has shown that the Mule Creek Obsidian Deposits were extensively mined and utilized by early cultures, and that the raw obsidian nodules and probably partially finished products (called blanks) were widely utilized and traded within in New Mexico and Southern Arizona. The evidence for this is based on analyzing the trace element composition of obsidian artifacts, and then comparing the results with the trace element composition of known obsidian source deposits.

cross-bedded rhyolite and perlite

Mule Creek cross-bedded rhyolite and perlite ash flow deposit

Extensive analysis of numerous obsidian source areas has shown that the type, amounts of, and the ratios of various trace elements within a source area are essentially unique, and thus can be used as a diagnostic tool for determining the source of the material used in an artifact’s manufacture, as well as providing clues as to distribution patterns and possible trade routes for the raw material.

Today obsidian is still used in the manufacture of precision cutting tools such as scalpels used in surgery. The reason for this is that a fractured edge of obsidian is far sharper than any surgical steel blade manufactured. Research on the effectiveness of obsidian scalpels has shown that wounds heal faster, with less scarring, and without complications.

The use of obsidian in jewelry, stone carvings, and sculptures goes back for thousands of years and continues today, where it finds abundant use in inexpensive, mass-produced jewelry, as well as high-end artisan jewelry, and as a carving stone for sculptures.
 

MULE CREEK OBSIDIAN AT THE HIGHWAY’S EDGE

mule creek, new mexico, obsidian

Close up of Marekanites in alluvium, weathered out of Mule Creek rhyolite and perlite ash flow deposit

For travelers who delight in taking the road less travelled, the most scenic route between the southern Arizona cities of Tucson and Phoenix and Casitas de Gila Guesthouses involves a spectacular one-hour drive through the Apache National Forest in Arizona and the Gila National Forest in New Mexico over AZ/NM Highway 78. About five miles east of the Arizona/New Mexico border, NM 78 passes through the small community of Mule Creek, which has a US Post Office (at least at the time of this writing), but no other stores. Near the sign for the post office there is a dip in the road where the typically dry Mule Creek crosses the road. For the traveller in a hurry, a one-minute stop here at the side of the road will almost always produce a couple of nice Marekanites left behind by short-term flooding of Mule Creek during periods of high runoff from the surrounding hills. For the more serious rockhound or geology afflicted souls, rest assured that longer visits into the surrounding Gila National Forest in this area can provide anywhere from a day to a lifetime of memorable geological experiences!
 

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CASITAS DE GILA GUESTHOUSES & ART GALLERY
50 Casita Flats Rd • PO Box 325 • Gila, New Mexico 88038
575-535-4455

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