Mack Mine (Mac), Rincon District, San Diego Co., California, USA

On the beryl-rimmed rebecs of Ruby
Brought fresh from the hyaline streams,
She played on the banks of the Yuba
Such songs as she heard in her dreams.
—Thomas Holley Chivers (1807–1858), Lily Adair.

The Mack mine is located in the SW4SW4 Sec. 25, T10S, R1W, SBM. The main workings are situated low on a hill slope east of the San Luis Rey River Valley, approximately 1.5 miles south-southeast of Rincon. The deposit was first described as 5 to 6 feet wide pegmatite dike with granite footwall and diorite hanging wall. The chief product was gem quality beryl of various colors, some of it deep blue. Small blue crystals of spinel have also been reported.

The deposit was one of the earliest sources of gem quality beryl in San Diego County, and was discovered in November of 1903 by John M. Mack[1] and local Indian J. Calac[2]. Mack and Calac worked the deposit for several years, but would not disclose the exact quantity of production, or provide detailed information regarding the number of specimens or cut stones sold.

In 1905, George Kunz reported several pounds of opaque deep blue beryl extracted, as well as several fine gem beryls, found in several colors including yellow, green, and deep blue. Kunz reported that many fine gems were cut from the clear crystals, with clouded ones cut as cabochons that displayed a pleasing cat's-eye effect. The mine was developed by 3 open cuts, the largest measuring 61 feet long, 32 feet wide, and 16 feet deep. The mine workings were located on both walls of a small arroyo, a few hundred feet northwest of the ranch house. By 1951, these workings were reported as slightly caved and overgrown with chaparral, while the dumps in the arroyo bottom had been mostly removed by flash floods.

The Mack pegmatite dike strikes north 15 degrees west, and dips about 40 degrees southwest. The vein is exposed continuously along strike for about 170 feet, and discontinuously to the south-southwest for 120 feet. The dike is about 2 feet thick for most of its length, and its maximum thickness is 3.25 feet. The pocket pegmatite comprises the lower 4 to 6 inches of the quartz-perthite pegmatite core, and the upper 6 inches of the underlying line rock.

The core zone contains numerous vugs which are lined with euhedral crystals of muscovite, albite, quartz, beryl, and garnet. The beryl crystals are greenish blue to blue, and measure up to 13mm in diameter.

By 1951, the Mack mine and the Calac ranch were reported to be privately owned by Charles W. Hall of Valley Center. Around this time, Frederick J. Rynerson reported that the "John Mac Mine" had produced more beryls than any other pegmatite mines in the region that he knew of, taking into considering the amount of work done developing the deposit.

Footnotes:

1. Macedonio Llora Merrion Machado, "Mac" (1857-1942), was born on the old Machado family homestead in Los Angeles County. Mac attended Santa Clara College and Heald's Business College in Los Angeles, and moved to Temecula in 1887 where he worked as clerk in the old government store in charge of Louis Wolf. Around 1889, he became owner of Machado & Co., a general store located downtown along the main street. In addition to his mercantile business, Mac had real-estate and mineral interests. Mac owned four hundred acres of land, and interest in twenty-five hundred acres of farming land within Riverside County. He also owned large interests in the tourmaline and beryl mines at Rincon and Smith mountain (Aguanga). Mac also owned a then-famous granite quarry near Temecula, where slabs of beautiful gray granite were cut and hauled by wagon or shipped by way of rail to their destination. While living out his life in Temecula, he also served two terms as chief ranger, four years as deputy assessor, a year as game warden, and one and a half years as postmaster. Although his surname was Machado, most people only knew him as "Mac". It is likely he occasionally used the informal English name of "John" for reasons of Spanish anonymity, and Anglo-Saxon congruence, which was common practice during the early 20th Century.

2. Also known as Feliz Calac. According to J. B. Hanley, an agreement was made between John Mack and Feliz Calac, to mine for gemstones occurring on Calac's ranch, which was described in 1958 by F. H. Weber as patented ranch land.

References:

Driggs, T. A. 2003. The Old Spanish California Machado family; Macedonia Llora Merrion Machado "Mac" and Dora Alice Vaughn "Allie". [http://freepages.genealogy.rootsweb.ancestry.com/~hindorff/M.Machado.htm]

Guinn, J. M. 1907. A History of California: Historical and Biographical Record: Macedonia Llora Merrion Machado. Historic Record Company, Los Angeles, Cal.; Volume 1, page 1027:

Hanley, J. B. 1951. Economic Geology of the Rincon Pegmatites, San Diego County, California. Department of Natural Resources, California Division of Mines, Special Report 7B: 24 pages, illus., maps.

Kunz, G. F. 1905. Gems, jeweler's materials, and ornamental stones of California. California State Mining Bureau bulletin 37: p. 50, 137-139.

Merrill, F. J. H. 1914. Geology and Mineral Resources of San Diego and Imperial Counties: Gems, Lithia Minerals. California State Mining Bureau, San Francisco, Cal. California State Printing Office, December. Chapter 1, pages 61-110.

Rynerson, F. J. 1967. Exploring and mining for Gems and Gold in the West. Happy Camp, California: Naturegraph Publishers, Inc.: p. 198.

Weber, F. H. 1963. Geology and mineral resources of San Diego County, California. California Division of Mines and Geology, County Report 3: p. 106, illus., maps.