Mining activity in the Ray District began with the location of silver and copper claims in the 1870s. And the discovery of placer gold found at the Steamboat Wash Placers along the Gila River in the early 1880s heightened interest in the area.
Organized with British capital in 1899, Ray Copper Mines Ltd., took a stake along the confluence of Mineral Creek and the Gila River when it established the milling town of Kelvin, named for William Thompson Kelvin, a British mathematician and physicist. The site originally hosted the small stage-stop town of Riverside, created in 1877. A 250-ton concentrator, along with shops, offices and staff buildings, was erected onsite.
The town received shipments of copper ore from the Ray Mine by a 5½-mile-long, 30-inch-narrow-gauge railroad completed in April 1900 on the east side of Mineral Creek. It connected the mine to the mill.
An average of 70 tons of ore could be transferred between both every hour.
The route was originally surveyed by Herbert Pinckney Winslow in 1899. A smelter was also built at Kelvin, which treated 16,000 tons of ore.
By 1902, the population of Kelvin reached 1,000.
However, challenges with the mill’s construction and equipment, along with the lack of profitably involved in treating low-grade copper ore averaging 2 percent, prompted the British investors to abandon the project.
In 1903, Kelvin processed ore from the Troy-Manhattan copper mines that operated 8 miles northeast. The camp of Troy, known earlier as Skinnerville, consisted of 200 people.
It was considered a role model of mining camps because its citizens prohibited the establishment of saloons. The camp included a municipal water system, along with a general store, boarding and school houses, assaying buildings and a library housed in a union hall built by the Troy Miners’ Union.
A narrow-gauge railroad transported copper ore for processing at Kelvin.
This train had a toy-like appearance, and its largest feature consisted of a smokestack. Its cars could hold up to eight men.
The Utah Copper Co. became interested in the Ray deposit after having successfully undertaken mining low-grade, disseminated copper ore through open-pit mining at Bingham Canyon, Utah.
An option on the property was secured in 1906 by American investors, including Daniel C. Jackling, progenitor of the open-pit mining concept. Two companies were formed: the Ray Copper Co., and the Gila Copper Co.
In 1910, the two companies combined to form the Ray Consolidated Copper Co., also known as “Ray Con.”
Kelvin’s prominence waned upon the establishment of the smelter town of Hayden at the confluence of the Gila and San Pedro rivers in 1909. Yet, mining activity continued nearby with the Kelvin-Sultana Copper Co., incorporated in 1910 — and later reorganized as Ray Boston Copper Co. — worked the Riverside and Bryan group of mines, encompassing 6,500 feet of workings less than 2 miles southeast of Kelvin.
A 50-ton mill was erected near Kelvin in 1917 by the U.S. Vanadium Development Co., which processed deposits of vanadinite in granite associated with wulfenite.
Located on the company’s claims, these ore deposits averaged 4 percent vanadinite.
During the 1970s, the Cities Service Minerals Corporation conducted a series of exploration programs involving ground-magnetic surveys, geochemical analysis and drilling around the Kelvin Mineralized Zone. Findings at the site 5 miles south of the Ray Mine confirmed a large porphyry copper sulfide deposit (aptly named the Kelvin Deposit) at depths greater than 1,700 feet with a copper reserve in excess of 1.2 billion pounds.
