It is time now to select the stone! What to look for? Two things: absorbency and acid sensitivity. You do NOT want a “granite” too darn absorbent, and you do NOT want a “granite” that is mixed with calcite (the main component of marble and limestone.) And here comes my little “lemon juice (and oil) test” to the rescue! Since you can’t get the true geological name of the stones you brought home with you (nor do you probably care to!), what you want to know is which one is going to make you happy. Line your samples up on a table or countertop, dust them thoroughly, then spill a few drops of lemon juice and cooking oil on each one of them. If you notice that where the juice and the oil hit the stone its surface turns dark just about immediately, take those scraps and dump them in the garbage can (where they belong) without a second thought! If you notice that the juice and the oil take a little time to get absorbed (a half a minute or better), then you have a stone whose absorbency can be effectively controlled with a good-quality impregnator. If you finally notice that some samples will not absorb anything within, say, half an hour or so, then you may have a winner right there! That stone will not even need to be sealed! Now, how to eliminate the word "may" from the equation? The answer resides in another question: Why use lemon juice instead of, say, plain water? Because, like I mentioned above, you’re not just looking to determine the absorbency of the stones you’re considering, but you also want to determine that your samples are 100% silicate rocks (whether true granite or not), as opposed to some stones – still traded as granite – that are mixed with various percentages of calcite. If there’s even a little calcite in the stone, it will react to the high acidity of the lemon juice (citric acid) and, when you wipe your spills dry, you will notice a dull spot the same shape as the drops of lemon juice. In that case, once again, off to the trash they go! If, instead, it’s still nice and shiny where the drops were, then you have eliminated the "may" factor!
This simple but effective test to select granite for your kitchen countertops was originated by Maurizio Bertoli (1948-2009), a spunky, outspoken, told it like he saw it, whether you liked it or not, but respected and renowned authority on natural stone care and restoration.