Trade in worked ivory is complicated because of CITES regulation. The only elephant ivory that can be legally sold is that that has been worked, that is carved, before 1947. All trade in unworked ivory is banned. But, there are huge quantitities of tens of thousands of year old mammoth ivory that can be legally sold. We can distinguish between mammoth and elephant ivory from their patterns of Schreger lines. The Schreger are the cross-hatched lines that are best seen in ivory cut at 90 degrees to the length of the tusk. A scientific paper on the angle of intersection of the lines found that the 90 degree-cut mammoth lines generally cross at an angle of less than 90 deg whereas elephant ivory at generally more than 115 deg.
from THE HISTORY AND SIGNIFICANCE OF THE SCHREGER PATTERN IN PROBOSCIDEAN IVORY CHARACTERIZATION
EDGARD O'NIEL ESPINOZA, & MARY-JACQUE MANN
JAIC 1993, Volume 32, Number 3, Article 3 (pp. 241 to 248)
Below is a photo of the base of an 1850 Jaques king, with rather diffuse Schreger lines crossing at an obtuse angle (Left), and the base of a modern king made from mammoth ivory, with sharp Schreger lines crossing at a more acute angle (Right).
