. . .

The Weight of the Plates

It is impossible to calculate the exact weight of the plates. Also, the Small Plates of Nephi may have been of a different alloy than those made by Mormon, who leaves some doubt as to whether he himself manufactured the plates he used or wrote on plates previously made by another.

Joseph Smith said the plates were 6”x8”x6”, in which case they were 288 cubic inches in volume. Others have given different dimensions which would amount to volumes ranging from 244 to 336 cubic inches. The Prophet’s figure are preferable, since they represent an average and since he was more familiar with the plates than anyone else. A solid block of gold totaling 288 cubic inches would weight a little over 200 pounds. (Gold weights .697 pounds per cubic inches; silver, .379 pounds; and copper, .321 pounds.)

But plates would weigh much less than a solid block of the same metal. The unevenness is left by the hammering and air spaces between the separate plates would reduce the weight to probably less than 50 per cent of the solid block.

Also, as concluded above, the plates were not made of pure of 24-carat gold. It seems probable, on the one hand, that they were not made of extremely low-gold alloy because of the danger of electrolysis and brittleness. On the other hand, they were probably not of an extremely high-gold alloy eight, since the weight would thereby be increased, as well as the danger of distortion while being inscribed, due to the ductility of these higher alloys.

If the 8-carat gold alloy suggested by Widtsoe and Harris for the plates of Mormon be assumed, then, using the gravimetric system of Dr. Root, the plates would consist of 25.79 pounds of gold, occupying 37 cubic inches of the block; 77.84 pounds of copper, occupying 242.5 cubic inches; and 3.25 pounds (3 per cent added as an impurity), occupying 8.5 cubic inches.

A block of tumbaga, then, of the dimensions indicated for the plates of the Book of Mormon and with 8-carat alloy and 3 per cent native impurities, would weight 106.88 pounds. Using such a block as a beginning point, 50 per cent of the weight should be subtracted for air space, and the weight of the stack of plates would then be about fifty-three pounds. If these figures seem unrealistic, remember that gold is of twice the density of copper and would therefore occupy about one-sixth of the total volume.

If each plate were .02 of an inch thick it would occupy up to some .05 of an inch in the stack, or there would be twenty plates to the inch. The unsealed portion would then consist of forty plates or eighty sides. Present-day food cans are manufactured of metal which is about .01 to .015 of an inch think. How this compares with the “common tin” referred to by the Prophet remains to be investigated.

In the event the plates had been manufactured from a 12-carat gold alloy, they would have weighed 86.83 pounds, using the same system used for the 8-carat postulate. As the proposition of gold in the alloy is increased, so is its weight and ductility and the tendency of the plates, if hammered very thin, to distort and wrinkle.

Conclusion

We must conclude that early American metalsmiths had sufficient knowledge and skill to make a set of lates using the alloy called by the Spaniards, tumbaga. The plates of the Book of Mormon, we assume, were of this alloy and probably of between 8- and 12-carat gold. They thus appear to have weight between 53 and 86 pounds. We further assume that the plates were manufactured by hammering to a thickness of .02 of an inch, with a 23-carat gilded surface of .0006 of an inch, which thus presented a thirty-brinell hardness to the engraver’s tool, while the center of the plate maintained a brinell of eighty or above.

The plates themselves would have presented a solid gold surface to the eye, yet would have weighed as little as half what pure gold would have done.