Gardner F. Williams, American mining engineer, was the eldest son of Alpheus Fuller Williams and his wife Ann K. Simpson. After obtaining the degree Bachelor of Arts (BA) at the College of California (precursor of the University of California) in 1865, he qualified as a mining engineer at the Bergakademie (Mining Academy) at Freiburg, Gernamy, in 1868. Upon returning to the United States he continued his studies at the University of California and obtained the degree Master of Arts (MA). In 1870 he was appointed assistant assayer in the United States Mint at San Francisco, but from 1871 he worked as mill superintendent at Pioche, Nevada, for more than three years and then at Silver Reef, Utah. From 1875 to 1880 he was consultant for a New York exploration company and from 1880-1883 visited many mining regions in the western United States. In October 1871 he married Fanny M. Locke, with whom he had three surviving daughters and a son. The latter, named Alpheus Fuller Williams* like his grandfather, followed in his father's footsteps.
In 1884 Williams was appointed manager of the gold mines of the Transvaal Gold Exploration and Land Company at Pilgrim's Rest, in the South African Republic (Transvaal), but the venture was unsuccessful. He resigned this post in August the next year and returned to California, travelling on the same ship as the British imperialist and financier Cecil J. Rhodes. When Williams returned to South Africa in 1886 as the representative of an American mining concern, Rhodes asked him to become general manager of the De Beers Mining Company in Kimberley. He assumed duty on 1 May 1887 and assisted Rhodes in the amalgamation of the diamond mines and the formation of the De Beers Consolidated Mining Company in March 1888. A paper by him on "The diamond mines of South Africa" was published in the Transactions of the American Institute of Mining Engineers in 1887. He held his post as mining engineer and general manager of the company until his retirement in 1905. During this period he was responsible for introducing proper shaft sinking methods and an excellent system for training apprentices. In 1895 he presented a collection of rocks from the Kimberley area and De Beers mines to the South African Museum in Cape Town.
Williams was a strong supporter of the South African School of Mines, established by the South African College, Cape Town, which provided practical training in Kimberley from 1896 to 1903. He was chairman of its management committee in Kimberley during this entire period and in 1898 and 1899 was an examiner in the subject mining for the University of the Cape of Good Hope (which set the examinations for the SA School of Mines). In 1902 he published an authorotative work, The diamond mines of South Africa (New York, 1902, 681p; revised and enlarged ed., 2 vols, 1905). In this book he provided a full description of the mines and the principal diamonds recovered from them, the practice of underground mining, mining machinery, and the cutting and polishing of stones. Other publications by him included a paper on "The genesis of the diamond" in the Transactions of the American Institute of Mining Engineers (1904); a chapter on "The diamond mines of Kimberley" (mainly their geology) in Science in South Africa, a book published in preparation for the joint meeting of the British and South African Associations for the Advancement of Science in 1905; and a paper on "Mining methods at Kimberley" in Mining Magazine (1915).
Williams was a member of the South African Association of Engineers and Architects during the late eighteen-nineties. In 1902 he became a foundation member of the South African Association for the Advancement of Science, serving as joint vice-president from its inception and as president when the association held its fourth annual congress in Kimberley in 1906. In 1905 he became a member also of the British Association for the Advancement of Science.
In 1905 the Swedish Royal Academy of Sciences awarded him their silver medal. He retired at the end of that year and returned to the United States, settling in Washington, DC. There he presented a collection of rocks illustrating the occurrence of diamonds in South Africa to the United States National Museum. In 1910 an honorary Doctor of Laws (LLD) degree was conferred upon him by the University of California. At that time he still served on the council of the South African Association for the Advancement of Science. He moved to San Francisco in 1914.