Harmony Borax Works - Death Valley National Park EarthCache

Welcome to Death Valley

Welcome to Death Valley, one of the hottest and driest places on Earth. Despite these extreme conditions, this valley has long held natural treasures that shaped both geology and human history. One of the most important resources once mined here is borax, a mineral that was critical in the late 1800s for uses ranging from household cleaning to glassmaking. The Harmony Borax Works, located near Furnace Creek, became the center of this early industry. This EarthCache will guide you through the geology that created borax deposits in Death Valley, why this location was chosen for mining, and how the mineral’s story connects Earth processes to human ingenuity.

This EarthCache was created in correspondence with and with permission from the Death Valley National Park Service. Respect and follow all park regulations during your visit. Please help protect Death Valley by picking up your trash, staying on designated roads, and never feeding wildlife.

The Story Behind the Harmony Borax Works

The story of borax in Death Valley begins with the valley’s unique geologic setting. Death Valley is a graben, a block of Earth’s crust that has dropped down between mountain ranges along normal faults. Over millions of years, the basin filled with sediments eroded from the surrounding mountains. During wetter periods of the Miocene and Pliocene epochs, water pooled in this lowland, creating ephemeral lakes that repeatedly formed and dried up. These closed-basin lakes had no outlet to the sea, which meant that every mineral carried in by streams and groundwater remained behind after evaporation. This constant cycle of filling and drying concentrated salts and other dissolved materials to levels far higher than would be possible in open systems. Among the dissolved elements was boron, released from volcanic rocks and ash layers in the surrounding highlands. As groundwater and surface runoff leached boron out of these rocks, it was carried downslope into the valley, eventually becoming highly concentrated in lake waters and muds. As these lakes evaporated under Death Valley’s relentless heat, the chemistry of the remaining brines changed. The most soluble salts, such as sodium chloride, were among the first to crystallize. As evaporation continued and concentrations increased, boron combined with sodium, calcium, and water molecules to form borate minerals. Two of the most common borates in this region are ulexite and colemanite. Ulexite, sometimes nicknamed “TV rock” because of its natural fiber-optic properties, often appeared in cottony white masses near the surface of the playa muds. Over time, some of the ulexite was altered underground into colemanite, a more stable calcium borate mineral. The result was a network of borate-rich layers interbedded with clays, silts, and volcanic ash deposits that together make up the Furnace Creek Formation. These sediments, now tilted and exposed by faulting and erosion, are the source of the deposits that early miners discovered.

What makes the Harmony Borax Works site especially significant is not only the presence of borates but also their accessibility. In much of Death Valley, borates remained locked below surface layers of clay or gravel. Here, however, erosion had stripped away some overlying sediments, leaving the whitish borate “cottonballs” visible on the surface. To miners of the 1880s, these light-colored patches stood out starkly against the darker badlands of the Furnace Creek area, signaling the presence of a valuable resource. The geology determined not only the location of borates but also how feasible it was to extract and process them. Without the interplay of tectonics, volcanism, chemical weathering, and evaporation in a closed-basin desert, the borax industry of Death Valley could never have existed. These deposits also provide geologists with an excellent record of past climates and lake environments, illustrating how faulting created the basin, volcanism supplied boron-bearing rocks, and evaporation drove the crystallization of borates. Together, these forces made one of the richest borate deposits in North America and set the stage for the history that unfolded at the Harmony Borax Works.

Tasks for This EarthCache

To log this EarthCache, visit the site and complete the following tasks. Send me your answers via Geocaching or email.

1. Include "Harmony Borax Works - Death Valley National Park - GCBCGTE" on the first line of your message.

2. Observe the soil near the ruins. What colors are the sediments around the ruins? How would you describe their texture? Based on these observations, what materials do you think the soil is made of?

3. Search for lighter-toned white borate deposits in the soil and describe their appearance. Why do you think borax is more visible here than in the nearby darker badlands?

4. Imagine the ancient lake that once existed here. Why would evaporation in Death Valley’s climate cause borax to crystallize?

5. In your log, attach a photo of yourself or a personal item with the Harmony Borax Works ruins in the background. (Note: photos predating the publication of this EarthCache are not accepted.)

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