Boron Borax Mine, Twenty Mule Teams and Trona

Boron, in Kern County along Highway 58, is the site of U.S. Borax's open-pit borate mine, which Rio Tinto owns. As of November 2026, you can look into the pit for free from the Borax Visitor Center, open Tuesday through Saturday. To the north, the town of Trona sits beside Searles Lake in the Searles Valley, where minerals come from underground brine. The twenty mule teams, later a symbol of the borax industry, hauled borax from Death Valley to the railroad at Mojave from 1883 to 1889.

What is mined at Boron, and what are borates used for?

Borates are minerals and compounds that contain boron. U.S. Borax's Boron operations page says the site holds more than 80 minerals. Industry wants four of them most: tincal, kernite, ulexite and colemanite.

Borates end up in many everyday products. Rio Tinto names fertilizer, glassmaking, wood protection and fiberglass insulation among them. The USGS 2026 boron summary says glass and ceramics are still the biggest U.S. users. It also notes boron joined the federal critical minerals list published in November 2025.

How big is the Boron borax mine?

These figures come from the company:

U.S. Borax describes the pit as the largest open pit mine in California. Rio Tinto shows 100% ownership. Finished product moves through the company's Wilmington site at the Port of Los Angeles, which Rio Tinto says has run without a break since 1924.

Can you visit the Borax mine in Boron?

Yes, through the visitor center. The mine is a working industrial site, so stay in the public area.

The U.S. Borax Visitor Center page lists these details as of November 2026:

• Address: 14486 Borax Road, Boron, CA 93516
• Hours: Tuesday through Saturday, 9 a.m. to 5 p.m.; last entry 4:45 p.m.
• Closed: Sundays, Mondays and major holidays; opening depends on the weather
• Cost: Admission and parking are free, and RVs fit
• Inside: Geology and history displays, a video theater, a gift shop and an ADA-accessible overlook of the operation
• Contact: (760) 762-7588 or [email protected]

The center was built in 1997. According to the Borax Visitor Center Foundation, gift store proceeds and visitor donations, along with employee and company gifts, pay for yearly local grants and scholarships.

There is also something new to see. On March 31, 2026, U.S. Borax unveiled a restored twenty mule team wagon set at the visitor center, now sheltered under a new cover. A historical marker erected in 2026 says the displayed set came from a blacksmith shop in Daggett, and that some original outfits were later reused to haul borate from near Calico to Daggett.

What were the twenty mule teams?

The National Park Service tells the story on its Twenty Mule Teams page. The teams worked for six years, 1883 to 1889. They carried borax from Harmony Borax Works, near Furnace Creek in Death Valley, to the railhead near Mojave.

• Distance: About 165 miles; a one-way trip took around ten days
• Pace: 17 miles a day at most
• Team: 18 mules plus 2 horses, run by a muleskinner and an assistant called a swamper
• Wagons: About 36.5 tons when loaded; the back wheels were 7 feet tall
• Season: The teams rested from June through September, when temperatures could hit 125 degrees

Harmony Borax Works shut down in 1888, after owner William T. Coleman's business empire failed. NPS says the twenty mule team became a symbol of the U.S. borax industry.

You can still see an original-style wagon in Death Valley National Park. The NPS Harmony Borax Works page describes an easy 0.4-mile round-trip walk past adobe ruins and a wagon, 1 mile west of Furnace Creek on CA-190. NPS advises against hiking there after 10 a.m. in summer.

What is Twenty Mule Team Road in Boron?

Twenty Mule Team Road runs through Boron, beside the Highway 58 freeway. AARoads explains that Highway 58 took over from U.S. 466 between Bakersfield and Barstow in the 1964 renumbering, and that old 466 pavement survives near the Twenty Mule Team Road interchange west of town. AARoads also shows the Borax Road on-ramp signed as California 58 Business.

The volunteer-run Twenty Mule Team Museum is at 26962 Twenty Mule Team Road. The visitor center page notes the museum is not affiliated with U.S. Borax. A 2022 report in The Loop, the latest public update we found, placed it at Boron Avenue and Twenty Mule Team Road, with free admission and hours of 10 a.m. to 4 p.m. daily except major holidays. Call or check locally before you go.

What is trona, and where is the town of Trona?

Trona is a mineral as well as a town. The USGS classes it as a hydrous carbonate with the formula Na3(CO3)(HCO3)·2H2O. It is a natural source of soda ash (sodium carbonate). In the USGS 2026 soda ash summary, glass accounts for an estimated 45% of U.S. soda ash use.

The town of Trona lies in the Searles Valley of San Bernardino County, near Ridgecrest. Searles Valley Minerals says its plants there start with solution mining and process brine from Searles Lake. Products it lists include boric acid, sodium carbonate, sodium sulfate, sodium bicarbonate, specialty borax, sulfate of potash and salt.

What happened to Searles Valley Minerals in 2026?

It has been a year of big changes. Here is the timeline from public reports:

1. February 2026: A WARN notice said the company would idle its Trona and Argus operations starting April 8, 2026, with more than 350 jobs ending, Sierra Wave reported. A spokesperson told ABC7 the cut was driven by "prolonged market, cost, and regulatory pressures." ABC7 also reported the company planned to focus on boron.
2. September 15, 2026: Through its Chapter 11 case, the company signed a court-supervised Section 363 sale agreement with 5E Advanced Materials. The deal covered the Westend and Argus plants, roughly 9,000 acres of Searles Lake brine resources, the Trona Railway and the community's drinking water system.
3. October 2, 2026: 5E said the purchase was complete. The September release said Westend would keep making boron, sodium sulfate and specialty products, and that Trona's water service would not be interrupted.

As of November 2026, the October announcement is the latest public update we found. Neither release addressed soda ash.

How do you visit the Trona Pinnacles?

The Trona Pinnacles are a field of more than 500 tufa spires covering about 14 square miles of the Searles Lake basin. The Bureau of Land Management manages the site, which was named a National Natural Landmark in 1968.

• Location: About 20 miles east of Ridgecrest
• Access: BLM dirt road RM143 leaves SR 178 roughly 7.7 miles east of the Trona-Red Mountain Road junction and runs about 5 miles
• Vehicles: Most two-wheel-drive cars make it, but the road may close after heavy winter rain
• Facilities: A single vault toilet; no drinking water or trash pickup
• Camping: Dispersed camping, up to 14 days in any 28-day stretch

Keep to existing roads. The BLM warns that desert plants flattened by vehicles may need decades to grow back.

How do you get to Boron and Trona from the High Desert?

To Boron: From Barstow, take Highway 58 west past Hinkley to Kramer Junction, where it meets US-395. Boron is a short way farther west; Borax Road leads to the visitor center. If you are curious about Hinkley's own history, see our post on Hinkley's water contamination case.

To Trona: From Hesperia or Victorville, take US-395 north through Kramer Junction toward Johannesburg. Gribblenation's road history traces Trona Road from US-395 near Johannesburg into the Searles Valley. Services are limited, so fuel up first and carry water.

For more nearby outings, see Desert Route 66 day trips and High Desert hotspots close to home.

How Pleasant Hill can help

Pleasant Hill Real Estate Group works across the High Desert, from Hesperia to Barstow and beyond. You can search homes, request a free home valuation, or contact us. For questions about Highway 58 and US-395 areas, reach broker Dustin Bynum or Nancy Navarro in Hesperia.

General information, not legal, tax or lending advice. Rules, fees and rates change; confirm with the agency linked above or ask us. Pleasant Hill Real Estate Group · CA DRE Corp. #01997374 · AZ Entity Lic. #LC694532000 · Equal Housing Opportunity.