This excerpt recognizes that Lafferty/Abney mention gold in Texas:
Of other publications of older date, such as D. Woodman’s ”Guide to Texas
Emigrants;” David R. Edwards’s “The Emigrant’s, Farmer’s, and Politician’s
Guide,” provided with maps, the notes about the country west of the Pecos,
even west of the Colorado River, are perfectly worthless, the maps not much
better than fictions.
The life and adventures of L D. Lafferty, by A. H. Abney, claiming to be
truth, mentions the presence of gold in Texas. Other publications, though
some of them are quite interesting, do not extend their narratives west of the
Staked Plains, and state more the adventures of the parties (surveyors and
hunters) than the approximately correct (geographical, etc.) character of the
country.
Source: Geological Survey of Texas; Report of the State Geologist 1890. GoogleBooks