Why whiskey stones don't cool as well as ice.

While they sound like something you might find in the Skymall catalog, whiskey stones have been touted as a way to cool drinks without the annoyance of dilution that you get from melting ice cubes.  It's true that they don't dilute your beverage of choice, and you get to make jokes about having drinks "on the rocks".  However, for real physics reasons these stones just aren't that effective at cooling your drink down.  To see this, let's consider how much energy it takes to warm four of these stones from -40 \(^{\circ}\)C to room temperature (25 \(^{\circ}\)C).  Each stone is around 8 cm³, and granite has a density of 2.7 g/cm³, and the specific heat of granite is 0.79 J/gK.  Combining, that means that warming four of those stones to room temperature would take around 4400 J.

Now consider an equivalent volume of ice starting at 40 \(^{\circ}\)C.  Ordinary ice has a density of 0.917 g/cm³, and a specific heat of roughly 2.05 J/gK.  Warming four 8 cm³ ice cubes up to 0 \(^{\circ}\)C takes 2400 J.  However, converting ice from solid to liquid requires a latent heat, in this case 334 J/g.  So, just melting those ice cubes requires 9800 additional Joules.  Without even worrying about warming up the resulting water, the ice cubes are able to take up almost three times as much energy just by warming up to the melting point and melting.  So, while it's true that ice can dilute your beverage, it is much better at cooling things (if that's what you want to do), thanks to the latent heat, the energy required to change phases. 

A lack of understanding of specific heats and so forth is quite common.  Even the article I linked above about whiskey stones says "Another obscure advantage of whiskey stones is they freeze quickly. Granite ice cubes are ready to go after 20 to 30 minutes in the freezer, whereas water needs hours to freeze into ice cubes."  That's not an advantage - it tells you that the heat capacity of your whiskey stones is low compared to the water equivalent.