Concise Bible Dictionary:

The word nataph signifies “a drop” and is so translated in Job 36:2727For he maketh small the drops of water: they pour down rain according to the vapor thereof: (Job 36:27). Hence stacte is doubtless a spice that oozes from a tree in drops: it formed a part of the holy incense (Ex. 30:3434And the Lord said unto Moses, Take unto thee sweet spices, stacte, and onycha, and galbanum; these sweet spices with pure frankincense: of each shall there be a like weight: (Exodus 30:34)). The RV has in its margin “opobalsamum.” It is probably the gum from the storax tree, Styrax officinalis.

Jackson’s Dictionary of Scripture Proper Names:

a drop