Read the label on the "Trophy Rock" ..... the "Sea Salt" ... better known as NaCl (i.e plain white, table salt) content is between 91% and 95% of the weight of the "rock". The remainder are trace minerals, some as low as to have to be stated in ppm (parts per million) rather than percentage by weight because the amout is practically miniscule.
I am not knocking a product here. No doubt deer will come to the Rock and use it. I am of the opinion that there are better values. For about $.20/pound to $.25/pound (rather than $.00+/pound for the Rock) you can formulate a great mix that deer absoultely pound and is good for them ... 50# of trace mineral salt + 50# of di-calcium phosphate + 50# of high calcium content dairy cattle supplemental minerals. All of this is available at any decently stocked farm supply store.
I have used a mix identical or very similar to this for decades. I do not have photos avaiable to back up this result statement ... but trust me, deer in SE Alabama kill this mix. Some of the long time areas where I first started putting this out have been dug out so deeply that small deer will disapear in the pit that has been dug. On one hillside location, the deer have dug an "overhang" that is 3' or more deep into the hillside and 6'-8' in diameter.
put out aobut 1500-2000 pounds of this every off season on the 3150 acres where I hunt. I will not claim that one of the end results is "monster" racks. But for sure the deer are using these licks and getting some nitrition due to the calcium and phosphate that have been included. The NaCl is of very little nutritional value, but does serve to bring the deer to the lick. Use Trophy Rock if that's what you like to use, but for my money I'll stick with this mix.