Commentary for Exodus 35:24

כל מרים תרומת כסף ונחושת, “Every man who donated a gift of silver or copper, etc.” No doubt silver was more plentiful than gold, not to mention copper of which the people must have owned an abundance. Presumably, the gold owned by the people was concentrated mostly in the hands of the women who used it as jewelry, whereas silver and copper were used mostly by the men, both as tools and as coins, i.e. money. This is why in connection with the silver the Torah speaks of תרומה, an expression of raising, separating, whereas in connection with donations consisting of gold the Torah speaks of תנופה, something which is lifted up. When someone donates gold he considers himself as having raised himself to a higher level. The recipients of a gift consisting of gold generally make a point of lauding the generosity of the donor. Still, on occasion we find the word תנופה used in connection with copper vessels when there is a reason to emphasise the value of that particular item such as in 38,29 where the Torah in mentioning the total weight of the copper donated (which collectively represented substantial value) describes it as “seventy talents, 2400 shekel worth.” The copper in question was highly polished, capable of acting as a mirror, therefore it deserved to be described as נחושת התנופה. Copper of that quality was even rarer than gold.