I have some whisky rocks but I do not use them often. I decided to see just how much they would cool my whisky. I put 1 ounce of whisky in a rock's glass (glenmorangie rocks glass, as will be used in my "glass" experiment) and added 3 whisky rocks. details as follows:
Whisky temperature, room temperature and glass temperature: 65.3F
Whisky rock temperature: 6.0F
57.8F after 1 minute
58.0F after 2 minute
59.3F after 6 minute (already warming back up without moving or drinking the whisky)
59.8F after 8 minute
60.3 after 12 minutes
-this says that with each "rock", the temperature dropped about 2.5F but quickly warmed back up.
-more could be added to drop the temperature lower, but it would have taken 6 to drop the temperature 15F. That is enough if the room temperature is 65F to start, but not if it is 75 or 85F.
-a really thin glass may have made some difference, but I did not want to put these rocks into a delicate glass
-a more healthy dram, say 2 ounces, would only have dropped a little less that 4F in this same case (ignoring the thermal mass of the glass).
-the whisky did not really "taste or feel" colder.
hope this helps for those who want to know more about the whisky rocks!