CHURCH OF THE NATIVITY: HISTORY & STRUCTURE
QUSTANDI SHOMALI,
Associate Professor, Bethlehem University (Palestine)
The Grotto
The part of the Church of the Nativity with the greatest religious and historical significance remains the Grotto of the Nativity, the traditional site of Jesus’ birth. In the church, two
entrances now lead to the Grotto. Originally, in the fourth century, there was only one entrance to the grotto from the main body of the church. An altar was erected over the birthplace, and a fourteen-pointed silver star was embedded in the white marble to mark the traditional place of Jesus’ birth. It was lit by fifteen silver lamps representing the different Christian communities. Six of the lamps belong to the Greek Orthodox, four to the Catholics, and five to the Armenian
Orthodox. The star bears a Latin inscription: Hic De Virgine Maria Jesus Christus Natus Est - 1717. ) Here Jesus Christ was born to the Virgin Mary(.It was installed by the Catholics in 1717, removed by the Greeks in 1847 and replaced by the Turkish government in 1853. In 1944, the medieval mosaic in the apse above the altar was cleaned and three words of the Latin text of the Gloria in Excelsis “terra pax hominibus” were found and they are partly preserved.
Opposite the altar of the Nativity, three steps lead the visitor to the Altar of the Manger, the place where the Baby Jesus was laid after he was born. A third altar has been erected opposite the Manger. It is dedicated to the Wise Men. The grotto is almost rectangular in shape measuring some 12 m. by 3 m. (40X10 feet)
It is encased in white marble.
unesco.org/archi2000/pdf/shomali.pdf
While the manger may have been carved from the stone walls of the cave, unless the cave itself was marble, it was only the local stone. In the above description, they say that the Grotto is encased in white marble. They would hardly have brought marble in to encase a marble cave.
There are instances of marble caves in the Holy Land, but this is not one of them.
As for a shortage of wood, I found this article:
The cultivated olive was forbidden to be cut because of its economical importance, as documented in many regulations for the protection of the trees “Rabbi Meir said: every tree that does not bear fruit except the olive and the fig [may be cut]” (Mishnah Kila’im 6, 5).
However, wild olive trees were commonly used as wood for building, in the ancient periods.
gemsinisrael.com/e_article000008705.htm
So it appears there was no shortage of wood for building or making mangers for feeding animals. I’m sure a longer, more detailed search could find out more about the availability of wood in the times of Jesus, but I don’t believe there was a shortage.