Easton's Bible Dictionary (1897)
(Ezek. 1:4, 27; 8:2. Heb., hashmal, rendered by the LXX. elektron, and by the Vulgate electrum), a metal compounded of silver and gold. Some translate the word by “polished brass,” others “fine brass,” as in Rev. 1:15; 2:18. It was probably the mixture now called electrum. The word has no connection, however, with what is now called amber, which is a gummy substance, reckoned as belonging to the mineral kingdom though of vegetable origin, a fossil resin.
Smith's Bible Dictionary (1863)
(Heb. chasmal) occurs only in (Ezekiel 1:4,27; 8:2) It is usually supposed that the Hebrew word chasmal (denotes a metal) and not the fossil resin called amber .
Hastings' Dictionary of the Bible (1898) & Schaff's Bible Dictionary
AM'BER. Eze 1:4, Gen 1:27;Eze 8:2 (better electrum, or bright gold gum). Fossil gum, a beautiful bituminous substance, susceptible of a fine polish, varying in color, but chiefly yellow and orange. It is mined in Prussia, and also washed ashore by the waves of the Baltic Sea. The word here used probably denotes electrum, a metal composed of gold and silver and held in high estimation among the ancients. In the passages cited the allusion is simply to the color of amber, and does not necessarily imply that it is indestructible by fire.