Eucalyptus spp. of the family Myrtaceae --- I have at least Eucalyptus foccunda and Eucalyptus loxophleba as having the name York gum but there may be others.
This is an Australian wood that comes from a very small tree (15 feet to 45 feet tall, with diameter up to 18 inches). You only very rarely see it in lumber form ... it's mostly burl of the tree that is of interest.
my samples: NOTE: these pics were all taken in very bright incandescent lighting --- colors will vary under other lighting conditions
this is the lumber of the tree, purportedly, specifically listed as York gum / Eucalyptus loxophleba
burl listed as york gum / Eucalyptus loxophelba
a full burl that appears to have been finished and polished
burl and closeup
sliced burl cap ... back and face
burl pen blanks
burl turning stock
York gum pistol grips, finished and polished
burl handle and pen barrels
burl bowl (actually looks more like a platter to me)
burl bowl shot at a wood store. HUGE enlargements are present.
two views of a natural edge bowl listed as york gum burl, but I don't see even a HINT of burl anywhere. It MIGHT be york gum wood, but to me it looks like a more normal eucalyptus wood.