|Easton's Bible Dictionary|
Occurs only in Genesis 2:12, where it designates a product of the land of Havilah; and in Numbers 11:7, where the manna is likened to it in colour. It was probably an aromatic gum like balsam which exuded from a particular tree (Borassus flabelliformis) still found in Arabia, Media, and India. It bears a resemblance in colour to myrrh. Others think the word denotes "pearls," or some precious stone.
Noah Webster's Dictionary
1. (n.) An unidentified substance mentioned in the Bible (Gen. ii. 12, and Num. xi. 7), variously taken to be a gum, a precious stone, or pearls, or perhaps a kind of amber found in Arabia.
2. (n.) A gum resin of reddish brown color, brought from India, Persia, and Africa.
Int. Standard Bible Encyclopedia
del'-i-um (bedholach): The word occurs twice in the Pentateuch:
(1) in Genesis 2:12, in conjunction with gold and onyx, as a product of the land of HAVILAH (which see), and
(2) in Numbers 11:7, where the manna is likened to this substance in appearance: "The appearance thereof as the appearance of bdellium." The latter comparison excludes the idea of bedholach being a precious stone, and points to the identification of it with the fragrant resinous gum known to the Greeks as bdellion, several kinds being mentioned by Dioscorides and Pliny. It was a product of Arabia, India, Afghanistan, etc.
Bdellium (2 Occurrences)
Genesis 2:12 And the gold of that land is good: there is bdellium and the onyx stone. (KJV JPS ASV BBE DBY WBS NAS RSV)
Numbers 11:7 The manna was like coriander seed, and its appearance like the appearance of bdellium. (WEB KJV JPS ASV DBY WBS NAS RSV)