In the first Beis Hamikdash, the tables in the Beis Hamitbachayim were made of silver;1 in the second Beis Hamikdash they were made of marble.2 (However, even in the first Beis Hamikdash there were marble tables in other places,3 such as the table next to the ramp where they put the meat of the Korbanos until they were offered.4)

1 Divrei Hayamim I 28:16. The Passuk just mentions silver tables, without explaining what they were used for, the Mefarshim (Mefaresh, Radak, and Medrash Divrey Hayamim from R' Shmuel Masnos) explain based off of Yechezkel (40:39-41) where he mentions stone tables that the were used while skinning and cutting up the Korbanos, and say that these are the tables that we are referring to here as well (these tables of yechezkel correspond to the eight tables in the Beis Hamibachayim, see Rashi Yoma 16b).

The question arises why do the Mefarshim explain like this, and we have to say that the First Beis Hamikdash is different than both the second and the third, as in both of them these tables were made of stone, why don't they explain the Passuk as referring to the silver tables known to be in the second Beis Hamikdash, like the table next to the ramp where the Keilim were stored (Shekalim 6:4), or the table in the Ulam where the Lechem Hapanim was placed on before bringing it in to the Heichal, which according to some opinions was made of silver (see Tosafos to Menachos 99b)? This is especially problematic as this is not just a detail you can say they just changed, and the material of the tables were not part of the instructions handed down; we cannot say this, as the Passuk in Divrei Hayamim that mentions the silver tables is describing the details of the Beis Hamikdash that David told Shlomo, when he gave him the scroll of the Megillas Hamikdash!

One answer we can give is that the mefarshim would rather say that the Passuk in Divrei Hayamim is relying on a different Passuk in Tanach, rather than on something that is not mentioned in Tanach at all. Another (more probable) answer is that they want to explain the Passuk according to the opinion that the table in the Ulam was marble, and there was therefore only one silver table in the second Beis Hamikdash, while the Passuk mentions silver tables, more than one.

From the above it comes out that this is one of the changes that they changed in the second Beis Hamikdash to be like the third. There is also a reason for this change, as marble does not heat up, while metal does, and makes the meat spoil faster (See Yerushalmi Shekalim 6:3 and Bavli Tamid 31b).

2 Middos 3:5

3 See Mefaresh to Divrei Hayamim I 29:2
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4 Shekalim 6:4

    The Gemara in Zevachim (54a), when discussing that there was no yesod on the south and east sides of the Mizbeach, asks a question. If there was no yesod under part of the Mizbeach, how could a bird Olah be offered there? The bird Olah's blood must be sprinkled on the upper half of the mizbeach, and it was preferably offered on the southeast corner of the Mizbeach, but since there is no yesod, the blood is just going to go on the floor? The Gemara answers, that there was a piece sticking out of the Mizbeach in that corner, for the blood to go on. (This is how Rashi explains the Gemara. Rabbeinu Tam explains it differently.) Based on this Gemara, I have added this Piece to the Mizbeach.