This is a good article on mining in the Black Hills. Lots of different minerals have been mined - tin, beryl, lithium, gold, etc. Spodumene is the most widespread. Here are some extracts. IRIS is looking for spodumene. Personally I believe you have over reacted to the presence of Amblygonite. There have been. Number of mines with spodumene in the black hills.
“Lithium from the Black Hills occurs in spodumene, amblygonite-montebrasite, lepidolite and triphylite. According to Page et al (1953), the occurrence lithium minerals are strongly dependent upon the compositional zones and fracture units of the pegmatites. Spodumene has been produced from all zones, although amblygonite occurs only in the intermediate zones and lepidolite only from cores zones. Spodumene was first produced at the Etta pegmatite in 1898 and sent to Omaha for experimentation. During the 1920’s the Etta mine was the principal producer of lithium in the United States. Virtually every reference to lithium bearing pegmatites mentions the huge spodumene crystals at the Etta. Prior to their discovery at the Etta, two-foot spodumene crystals found in New England pegmatites were considered “enormous”. The first reference to the spodumene “logs” at the Etta was by Blake in 1883 (see the Harney Peak article in SD issue I). Frank Hess in 1939, investigating rare minerals for the Bureau of Mines described these incredible crystals:
Edison eventually discovered the lithium storage battery. This usage and other applications such as welding, pyrotechnics, photography, de-humidifiers, and specialty glass contributed to an increase in demand during the late 1800’s and early 1900’s (Hess, 1939). A. I. Johnson (1989) estimated over 50,000 tons of spodumene was mined from the Etta pegmatite. Lithium hydride was produced from Etta spodumene during World War II and used to inflate antennae carrying balloons sent up by downed pilots for rescue. During the war effort, about 15,800 short tons were produced from the Black Hills. The peak production year occurred in 1951 when 8,600 short tons were produced.
Other spodumene localities in the Hills include the Tin Mountain mine, which was also noted for large crystals. At this locality crystals up to 30 feet have been found. Crystals up to 20 feet occur at the Beecher Lode. Well-defined crystals up to eight feet occur at the Helen Beryl mine. At this locality Roberts and Rapp (1965) note that hiddenite – spodumene is suitable for “first quality faceted gem stones”. Kunzite has also been found at the Beecher and Tin Mountain pegmatites.
Amblygonite, another ore of lithium, was first produced from the Hills in 1905 (Guiteras, 1940). Although not as abundant as spodumene in the Hills, it was easier to extract the lithium from the amblygonite and thus was more desirable. The Beecher pegmatite was known to contain huge masses of amblygonite up to 200 tons. However, enormous masses up to 30 feet were found at the Ingersoll mine and up to 40 feet at the Hugo mine (Roberts and Rapp, 1965).
Lepidolite, according to Connolly (1929) was the third most important lithium mineral in the Hills. The primary use during this time was for lithium salts, although it was also used in specialty glass. Lepidolite was first mined in the Hills at the Ingersoll mine according to Page et al (1953) in 1922 but was not intensively mined until about 1936. Lepidolite from the Ingersoll was used for the seventeen-foot lens in the observatory at Mount Wilson, California (Clow, 2002). Lepidolite operations ceased at the Ingersoll in 1944. Over 8,000 tons were mined from the Ingersoll pegmatite. Other notable occurrences according to Roberts and Rapp (1965) include the Beecher, Tin Mountain, wood Tin, and the Hugo pegmatites.”
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