There are a few other tests that can be used to differentiate one or more common minerals. Because these are so rare, this property helps narrow the possibilities drastically when trying to identify an unknown specimen. Feel - Some minerals, notably talc and graphite, feel greasy or slippery when you rub your fingers over them. The greasiness occurs because bonds are so weak in one direction that your finger pressure alone is enough to break them and to slide planes of atoms past neighboring atomic layers. Taste - Geologists use as many senses as possible in describing and identifying minerals.
Taste is one of the last tests to be conducted, because some minerals are poisonous.
Sylvite, a mineral similar in all other properties to halite, tastes bitter. Taste is thus a diagnostic property because it distinguishes between these minerals. Reaction with Dilute Hydrochloric Acid - This is actually a chemical property rather than a physical attribute of a mineral. Carbon dioxide is liberated from the mineral and bubbles out through the acid, creating the fizz. This test is best performed on powdered minerals.