Rockhound Vacations – Campground

Filed under: Rockhound Travel — Gary January 24, 2010 @ 11:46 am

Since I travel a lot I and I find myself seeking this kind of knowledge, I thought I would make a new category for rockhounding vacations / travel.  As well if you have a special place you like to stay and rockhound please email me and I will post  Pictures are appreciated as well.

Rockhound Travel

Rockhound Travel

Rockhound State Park and Spring Canyon Recreation Area
Established in 1966, Rockhound State Park consists of the main park and the Spring Canyon Recreation Area. The main park includes a 30-site campground, hiking trails and a visitor center on the west slopes of the Little Florida Mountains. The Spring Canyon Recreation Area is a day-use area located across the valley in the foothills of the Florida Mountains and includes picnic sites and hiking trails.

Take a Hike
The park’s Thunderegg Trail (1.1 miles) and the Jasper Trail (.5 miles) provide access to spectacular wildflower displays in spring, mild autumn weather, and scenic views year-round.  Scattered along the trails and throughout the park are assorted volcanic rocks and silica minerals including quartz, chalcedony, agate, and common opal.

Desert Alive!
Every April, Rockhound State Park hosts Desert Alive!, a springtime celebration of the Chihuahuan Desert and the rocks, plants and animals found here. Join nature walks, take in displays and exhibits and learn all about natural and cultural history of this special place.

Getting There
To get to Rockhound State Park from Deming, take N.M. 11 south for five miles, and then go east on N.M. 141 for about nine miles.

Rockhound State Park lies in the Little Florida Mountains southeast of Deming, New Mexico (Fig. 1). It was established in 1966 as the first park in the United States that allowed collecting of rocks and minerals for personal use. Each visitor is allowed to collect as much as 15 lb of rocks and minerals from the 1,100-acre park; mineral dealers are not allowed to collect for sale. Rockhound State Park actually consists of two separate units, the main park and Spring Canyon Recreation Area (Fig. 1). Spring Canyon lies in the northern Florida Mountains, south of the main park, and is open for day use only from Easter through November.

Figure 1 – Location of Rockhound State Park.

Figure 1 – Location of Rockhound State Park.

The main park provides excellent views of the surrounding mountain desert. Basin and Range topography is easily seen in the distance. On a clear day the smokestacks of the Hurley smelter can be seen to the northwest. The Cobre Mountains form the far northern horizon behind the smokestacks. The Burro Mountains lie to the west-northwest; the Victorio Mountains lie to the west-southwest. The Florida Mountains lie directly to the south of the main state park; Florida Gap separates the two ranges. The Cedar Mountains lie to the south-southwest. The dark mountain north of Deming is called Black Mountain. Spring Canyon in the Florida Mountains is a sheltered canyon and offers solitude common to many canyons throughout the desert Southwest.

The Florida and Little Florida Mountains are typical of the mountain desert throughout southern New Mexico and Arizona. Elevations range from 4,400 ft along the foothills, where the state park is located, to 7,448 ft at Florida Peak in the Florida Mountains. Water is scarce and limited to wells and hidden springs, but be careful of thunderstorms and flash floods during the summer months! Despite the dry, seemingly inhospitable environment, life abounds. The area is home to many lizards and snakes, deer, antelope, coyotes, and small mammals such as prairie dogs, rabbits, badgers, and many birds. Mountain lion and desert bighorn sheep may be seen at the higher elevations of the Florida Mountains. A variety of plants thrive in this environment, including yucca, prickly pear cactus, barrel cactus, ocotillo, creosote bush, mesquite, and hackberry; juniper and scrub oak are common in the canyons.


Paleozoic through lower Tertiary sedimentary rocks overlie a Cambrian granitic to syenitic pluton in the northern Florida Mountains (Clemons and

Brown, 1983; Clemons, 1984, 1998). The rocks at Spring Canyon Recreation Area belong to the Starvation Draw Member of the Rubio Peak Formation and were emplaced about 51–36 m.y. ago (late Eocene to early Oligocene, Clemons, 1982). The Starvation Draw Member consists of volcanic breccias, conglomerates, and lavas of andesitic composition. A rhyolite dike, which cuts the Starvation Draw Member near the head of Spring Canyon, is 25.4 m.y. old (groundmass, 40Ar/39Ar; unpublished age determination, New Mexico Geochronology Research Laboratory, New Mexico Institute of Mining and Technology).

The Little Florida Mountains consist predominantly of interbedded mid-Tertiary andesitic, dacitic, and rhyolitic ash-flow tuffs and lavas, and volcanic-derived fanglomerates intruded by rhyolite domes and dikes (Fig. 2; Clemons, 1982, 1984, 1998). The earliest evidence of volcanic activity in the Little Florida Mountains are small outcrops of ash-flow tuffs exposed approximately 1 mile north of the state park (Fig. 2) and farther north, near Little Gap. Altered sanidine and biotite from an ash flow near the base of the stratigraphic section at Little Gap give 40Ar/39Ar ages of 33.5 m.y. and 32.9 m.y., respectively. This ash flow may correlate with the 33.5 m.y. old Oak Creek Tuff that erupted from the Juniper caldera in the northern Animas Range in the Boot Heel volcanic field in Hidalgo County to the west. During ash-flow eruptions, volcanic ash can travel a great distance from the source vent. In some cases, the ash is still very hot when deposited and can then fuse, or weld, into a very dense, hard layer of rock, such as the ash-flow tuff found in the Little Florida Mountains. The ash-flow tuff is overlain by andesite flows (andesite of Little Florida Mountains) that were probably erupted from shield or stratovolcanoes. The vents of these once-prominent volcanoes are difficult to impossible to find because of local faulting and rapid erosion. The andesites subsequently were intruded by rhyolite domes and covered by rhyolite lavas and tuffs (Fig 2; rhyolite tuff [Tlt] and rhyolite [Tlr] of Little Florida Mountains; Clemons, 1982). Volcanic activity was relatively brief in geologic time; rhyolite and andesite samples from the state park range in age from 28.5 to 24.4 m.y. (40Ar/39Ar; unpublished age determination, New Mexico Geochronology Research Laboratory, New Mexico Institute of Mining and Technology). Seismic data suggest that there are only 600 ft of volcanic rock in the subsurface in the area of the state park.

Figure 2 – Geologic map of the Little Florida Mountains, including Rockhound State Park (simplified from Clemons, 1982).

Figure 2 – Geologic map of the Little Florida Mountains, including Rockhound State Park (simplified from Clemons, 1982).

Erosion of the volcanic rocks began during and after eruption. The fanglomerate of Little Florida Mountains was the first of the deposits that formed by erosion of the volcanic rocks and is Miocene in age (Clemons, 1982; Kiely and James, 1988). Dacite flows were erupted onto the fanglomerate of Little Florida Mountains. During and after this brief period of volcanic activity, regional tectonics (i.e. mountain building by block faulting) related to the Rio Grande rift uplifted the Little Florida and Florida Mountains; erosion has since worn the mountains down to their present elevation above the surrounding desert. Wind, water, and ice have continued to break up the rocks through time and to carry fragments downslope forming the gently sloping bajadas or alluvial fans at the base of the mountains. The campground at Rockhound lies on one of these bajadas.

Geothermal ground waters and springs were associated with the volcanic activity. Silica cementation of the younger fanglomerate of Little Florida Mountains indicates that these fluids continued to circulate long after eruption of the volcanic rocks and during their erosion (Kiely and James, 1988). Manganese-oxide and fluorite veins that cut the fanglomerate of Little Florida Mountains in the northeastern part of the Little Florida Mountains were also formed during this time. These deposits are present where various manganese- and iron-oxide minerals, along with fluorite, barite, calcite, and quartz, are found in the fanglomerate of Little Florida Mountains (Lasky, 1940; Clemons, 1982; Kiely and James, 1988). Hydrothermal fluids that contained high concentrations of manganese and fluorite, along with silica, also formed these mineral deposits. The Manganese mine was one of the larger producing mines in the district. The mines are extremely unsafe, and visitors should not enter the adits. Care is needed around the shafts and prospect pits as well. Fluorite production from epithermal fluorite veins is estimated as 13,428 short tons, mostly from the Spar mine (McAnulty, 1978). Manganese production from epithermal manganese veins is reported as 19,527 long tons of ore and 21,393 long tons of concentrate (Farnham, 1961; McLemore et al., 1996). Production of manganese ceased in 1959 when the Federal government ended its buying program.

Mineral deposits were discovered in 1876 in the Florida Mountains district south of Spring Canyon in the main Florida Mountains. Hydrothermal fluids that created replacement deposits in carbonate rocks also formed these deposits. The hot fluids actually dissolved the limestone and dolomite in the carbonate rocks and left cavities that were later filled by precipitation of minerals from the fluids. From 1880 to 1956, 5,000 lbs copper, <10 oz gold, 8,000 oz silver, and >30,000 lbs lead worth approximately $102,000 were produced from carbonate-hosted Pb–Zn and polymetallic vein deposits in the district (McLemore et al., 1996). The Mahoney and Silver Cave mines were the largest metal producers. In addition, 200 short tons of fluorite and 1,421 long tons of 22–30% manganese have been produced from epithermal veins in the district (Farnham, 1961; McLemore et al., 1996).

The basins around the Little Florida and Florida Mountains subsided as the mountains were uplifted. Rain and snow melt from the local mountains, including the Little Florida and Florida Mountains as well as the Cobre Mountains and Black Range north of Deming, percolated through the rocks, migrated into the basins, and formed large reservoirs of ground water that we call aquifers. Today, this ground water is being pumped from the basins surrounding Deming faster than it can be replaced by current rainfall.

Formation of thundereggs and geodes

Gray perlite, thundereggs, geodes, jasper, onyx, agate, crystalline rhyolite, Apache tears (obsidian), and quartz crystals are among the more common rocks and minerals found in the park. Thompsonite, a zeolite, is found in amygdules in quartz latite (Northrop and LaBruzza, 1996). Agate is present in a wide range of colors and is one of the minerals that many visitors collect at Rockhound State Park. Some thundereggs and geodes found at Rockhound contain multicolored agate in addition to well-formed quartz crystals.

The difference between geodes, thundereggs, and concretions can be confusing. “Geodes” are hollow or near-hollow, crystal-lined cavities found in igneous and sedimentary rocks. “Thundereggs,” also known as spherulites, are solid or near-solid nodules formed by magmatic and volcanic processes and are found only in volcanic rocks (Lofgren, 1971). Spherulites are made of radial crystals extending from the center. Prehistoric Indians found solid nodules near Mt. Jefferson and Mt. Hood in Oregon and thought that when the gods or spirits who inhabited the mountains became angry with one another they would hurl nodules at each other with accompanying thunder and lightning. Hence they called these nodules thundereggs (Shaub, 1979). They range in diameter from less than 1/4 inch to greater than a foot. “Concretions” are compact accumulations of minerals cemented together to form hard masses in sedimentary rocks. Concretions can be hollow inside, and some concretions contain a loose “nut.” Concretions can be any shape or size, whereas geodes and thundereggs are typically rounded to slightly ovoid.

Many thundereggs found at Rockhound State Park are spherical and consist of two distinct parts: a dark-gray to pinkish outer part and a white, blue, or gray inner part, or core, which is recognizable as agate, chalcedony, and quartz crystals, all forms of the compound SiO2. In many examples, these two parts can be described as a shell and a filling. However, some thundereggs, or spherulites, do not contain the filling; they are composed of solid dark-gray to pinkish shell material (Fig. 3) or are partly hollow. Geologically distinct processes form the two parts of the thundereggs. The outer part of the thundereggs is formed by complex magmatic processes (i.e. as spherulites), and then the inner part is formed and modified by multiple cycles of late-stage hydrothermal fluids. The processes that form geodes and thundereggs are complex and are controlled by constantly changing physical and chemical conditions, such as temperature, pressure, depth of formation, composition of the magma, composition of the ground water, and composition of the host rocks.

Solid spherulite from Rockhound State Park

Solid spherulite from Rockhound State Park

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