This Black Hills gold is some very beautiful gold. I have always like this style. This gold is mixed with other ores that do the tarnishing . Please see the link below for more information. http://www.goldoutlet.com/history.html
Whether any gold tarnishes or not depends on how much gold is in the item. A low carat item - 6 or 8 carat - has a lot of other metals mixed with it. It's not the gold that tarnishes, it's the other metals.