מדרש על שמות 28:11

"Also the use of the Shamir had stopped." Our Rabbis were taught: The Shamir is that with which Solomon built the Temple, as it is said (I Kinfis 6, 7) And the house, when it was in building was built of entire stones, etc. R. Juda says: "This is to be taken literally." R. Nechemia said to him: "How is it possible to think so? Behold, it is said (Ib., 7, 9) All this were of heavy stones hewn after a fixed measure sawed with the saw inside and outside? We must therefore say that the meaning of the passage (Ib. 6, 7) [So that neither hammer, nor axe nor any tool of iron] heard in the house while it was in building, means that it was prepared outside and then brought inside." R. Nachman said: "The opinion of R. Juda concerning the stones of the Temple, appeals to me and likewise the words of R. Nachemia, as far as the stones of Solomon's own palace that every kind of tool was used." But according to R. Nechemia, then why was the Shamir necessary? The latter was necessary for the stones of Ephod, as we are taught in a Baraitha; The Stones of the Ephod, it was not written upon them with ink, because it is said (Ex. 28, 11) Like the engraving of a signet, nor was it marked with a cutting tool, for it is said Bemiluotham, which means that nothing should miss. We must therefore say that they wrote with ink on the stone and they brought the Shamir and the marks which were outside, were shown to it which caused the stones to split by themselves like a date which splits itself during the summer time and nothing is missing of it, or like the earth that divides itself during the winter time in places and nothing is missing. Our Rabbis were taught: The Shamir was created as big as a barley and she exists since the day of creation and no hard thing can withstand it. How is it preserved? She is kept covered with tufts of wool and placed in a leaden tube filled with barley bran.