According to Diane Wirth, a famous Swedish archaeologist, Sigvald Linne, found a piece of smelted iron in a tomb at Mitla, Oaxaca, Mexico. Yet the Smithsonian still claims no smelted iron was found in Mesoamerica. [Diane E. Wirth, A Challenge to the Critics, p. 28]
“Iron”
According to John Sorenson, iron use was documented in the statements of early Spaniards, who told of the Aztecs using iron-studded clubs. A number of artifacts have been preserved that are unquestionably of iron; their considerable sophistication, in some cases, at least suggests interest in this metal. . . . Few of these specimens have been chemically analyzed to determine whether the iron used was from meteors or from smelted ore. The possibility that smelted iron either has been or may yet be found is enhanced by a find at Teotihuacan near Mexico City. A pottery vessel dating to about A.D. 300, and apparently used for smelting, contained a "metallic-looking" mass. Analyzed chemically, it proved to contain copper and iron.
Without even considering smelted iron, we find that peoples in Mesoamerica exploited iron minerals from early times. Lumps of hematite, magnetite, and ilmenite were brought into Valley of Oaxaca sites from some of the thirty-six ore exposures located near or in the valley. These were carried to a workshop section within the site of San Jose Mogote as early as 1200 B.C. [John Sorenson, An Ancient American Setting for the Book of Mormon, F.A.R.M.S., pp. 284-285]
“Brass”
According to John Sorenson, a different alloy than "brass" is "bronze," made of copper with tin. The word bronze does not occur in the Book of Mormon, but "brass" does. The "brass plates of Laban" were brought from Jerusalem by Nephi, as we know. Until a few years ago it was supposed that what we call brass (an alloy including zinc) was developed only in the last few centuries. Yet the Bible speaks of "brass." Bible scholars have dealt with that apparent misstatement by saying that the word translated "brass" was actually bronze. The Hebrew word now known to refer to both copper and bronze was translated in the King James Version of the Bible as several different English words (in Ezekiel 1:4, 27 it comes out as "amber"). Within the last few years, however, some ancient artifacts from the Mediterranean area have been tested by more sophisticated scientific techniques than before, and the tests reveal that actual brass, with zinc in it, was in use among the Etruscans, probably as early as Lehi's time. That means that perhaps the brass plates of Lehi's day are neither an anomaly of cultural history nor an oddity of linguistic labeling, but of the literal metal.
Bronze was used in Mesoamerica, although its composition (that is, the proportion of tin) was not as standardized as in the Old World. [John L. Sorenson, An Ancient American Setting for the Book of Mormon, F.A.R.M.S., p. 283]