the translation of the Hebrew word Shamir in (Ezekiel 3:9) and Zech 7:12 In (Jeremiah 17:1) it is translated "diamond." In these three passages the word is the representative of some stone of excessive hardness, and is used metaphorically. It is very probable that by Shamir is intended emery, a variety of corundum, a mineral inferior, only to the diamond in hardness.
ADAMANT
Meaning of ADAMANT in English
Smith's Bible English dictionary. Английский библейский словарь Смита. 2012