According to Reed Putnam, Joseph Smith said, “In the bottom of the box were laid two stones crossways of the box, and on these stones lay the plates and the other things with them.” In view of this elevated setting on stone in a cemented stone box, one might ask, Did Moroni intend merely to hide the plates, or did he intend to preserve them also? The phrase “I seal up these records” (Moroni 10:1-2) could not have referred to the so-called sealed portion of the plates, but rather to the disposition of the entire stack. The sealing, then, must refer to the box in which the plates were deposited. Moroni was careful that no dirt or water should get to the plates, knowing that under certain conditions they could be damaged or destroyed. The title page of the Book of Mormon also indicates that the plates were “sealed up, and hid up unto the Lord, that they might not be destroyed.” [Reed Putnam, Were the Gold Plates Make of Tumbaga?,“ The Improvement Era, Sept. 1966: 788-9, 828-31. Reprint by F.A.R.M.S., pp. 3-4]
“And I Am the Same Who Hideth Up This Record Unto the Lord”
After writing an epilogue to his father’s abridgment (see Mormon 8:1-13), the amount of time that elapsed before Moroni returned to the sacred depository to once again take the stylus in hand is unclear. However, when Moroni returned to the sacred site and removed the plates of Mormon from their place of concealment. He engraved a brief affirmation that he was the same person who had previously buried the sacred records. He wrote: ”And I am the same who hideth up this record unto the Lord" (Mormon 8:14). Without that transitional sentence the reader would be lost as to who was writing on the plates following the previous benedictory conclusion.
According to Donl Peterson, from Moroni’s first epilogue (vv. 1-13) to this declaration ( v. 14--“I am the same who hideth up this record”) at least three things happened to Moroni: (1) he had procured more plates; (2) he had had some great and unusual spiritual experiences wherein he had seen in vision, among other things, the events that would transpire in the last dispensation; and (3) his writing style had changed to one of assurance and of confidence, which was noticeably lacking in his previous entry. [H. Donl Peterson, Moroni: Ancient Prophet Modern Messenger, p. 21]
“Hideth Up This Record Unto the Lord”
Joseph Smith described the plates as follows:
These records were engraven on plates which had the appearance of gold, each plate was six inches wide and eight inches long and not quite so thick as common tin. They were filled with engravings, in Egyptian characters and bound together in a volume, as the leaves of a book with three rings running through the whole. The volume was something near six inches in thickness, a part of which was sealed. The characters on the unsealed part were small, and beautifully engraved. (History of the Church, 4:537)
According to Reed Putnam, the term “appearance of gold” probably means that the plates were yellow in color but not pure gold. Tumbaga is an alloy of gold and copper, the only two colored metals known to man. The early American smiths used the alloy of tumbaga extensively. It ranged in content from 97 percent gold to the same proportion of copper, with several trace metals as impurities and silver as an impurity or deliberate alloy up to 18 percent.
Tumbaga, the magic metal, can be cast, drawn, hammered, gilded, soldered, welded, plated, hardened, annealed, polished, engraved, embossed, and inlaid. Once the gilding was applied, the result to the eye alone would be gold. Yet with all this versatility, tumbaga will destroy itself if it is improperly alloyed, improperly stored, or improperly finished. The plates themselves would have presented a solid gold surface to the eye, yet they would have weighed as little as half as much as pure gold. A block of tumbaga of the dimensions indicated for the plates of the Book of Mormon and with 8-carat alloy and 3-percent native impurity would weigh 106.88 pounds. But the plates would weigh much less than a solid block of the same metal. The unevenness left by the hammering and air spaces between the separate plates would reduce the weight to probably less than 50 percent of the solid block. Thus the weight of the stack of plates would be about 53 pounds.
If Mormon and Moroni hammered the plates to a thickness of .02 of an inch with a 23-carat gilded surface of .0006 of an inch, the resulting hardness would have been 30 Brinells to the engravers tool while the center of the plate maintained a Brinell of 80 or above. While the exact size of the engravings, or glyphs, and the distance between them and between the lines are not known, Putnam has a specimen of hand-engraved work in English that is very legible and in which the lower-case letters are less the 1/16 of an inch in height. [Reed Putnam, Were the Gold Plates Make of Tumbaga?," The Improvement Era, Sept. 1966: 788-9, 828-31. Reprint by F.A.R.M.S., pp. 3-4]
Note* According to John Sorenson, a tumbaga specimen from Belize (British Honduras) shows that this material was known in the Maya lowlands no later than the fifth century A.D. [John L. Sorenson, An Ancient American Setting for the Book of Mormon, p. 283]
Moroni 10:2 I seal up these records (Weight & Composition) [[Illustration] It is of interest that tumbaga was commonly gilded by applying citric acid to the surface. The resulting chemical reaction eliminated copper atoms from the outer .0006 inch of the surface, leaving a microscopic layer of 23-carat gold that made the object look like it was wholly gold. (Reed H. Putnam, “Were the Plates of Mormon of Tumbaga?” The Improvement Era, Sept. 1966: 788-9, 828-31, Reprint by FARMS; and Heather Lechtman, “Pre-Columbian Surface Metallurgy,” Scientific American 250 (June 1984): 56-63)
In the process of depletion gilding, the particles of gold and copper that are uniformly distributed throughout the alloy are exposed to an open flame, which causes the copper to turn black. The copper is then removed by a mildly acidic “pickle,” such as a citrus extract. When heated and polished, the remaining surface particles compress and form a thin layer of pure gold. [“Of What Material Were the Plates,” in Journal of Book of Mormon Studies, vol. 10, num. 1, 2001, p. 21]