3.6: Special or Unique Properties
Special or Unique Properties
Effervescence
Some minerals react when dilute hydrochloric acid (HCl) is placed on them (Figure 3.9). When hydrochloric acid is introduced to a mineral, like calcite Links to an external site., a carbonate mineral, a chemical reaction occurs. The mineral effervesces, fizzes or bubbles and releases carbon dioxide gas. When you test a mineral with acid, be cautious and use just a drop of the acid. Use your magnifying glass to look closely for bubbles. The acid is very dilute and will not burn your skin or clothing, but you should always wash your hands after use. Also make sure that you rinse with water and wipe off the acid from the minerals that you test. Occasionally, vinegar can also be used, but larger quantities are necessary and the reaction becomes muted.
Figure 3.9: Calcite reacting (bubbling) with the addition of dilute (1M) hydrochloric acid (HCl). (CC-BY 4.0; Chloe Branciforte, own work).
Magnetism
Certain metal bearing minerals will be attracted to a magnet. Magnetite Links to an external site., an iron oxide, is an important mineral in sea floor striping; stripes oriented parallel to mid-ocean ridges, which will be discussed more in Plate Tectonics.
Taste
Some minerals have distinct tastes, which can be useful in determining the mineral name. Commonly, the halides Links to an external site. can be tasted and, in the case of halite Links to an external site., taste familiar (it is common table salt!). Other salts will have more bitter or sweet flavors depending on the types. However, YOU SHOULD NEVER TASTE UNKNOWN MINERALS. Tasting unknown minerals is an unsafe practice, as there are many minerals that you should not ingest. Only taste minerals cleared by your instructor.
Smell
Commonly, sulfur Links to an external site. bearing minerals have a distinct rotten egg odor. This can be a clue to the chemical composition of the mineral, which points to specific mineral groups and eliminates others. When smelling minerals do not smell the mineral directly, instead waft Links to an external site. the smell to your nose.
Fluorescence
Fluorescent minerals are those that emit visible light when activated by invisible ultraviolet light (UV), X-rays and/or electron beams. Certain electrons in the mineral absorb the energy from these sources and jump to a higher energy state, this results in many of the dayglo colors (Figure 3.10).
Figure 3.10: Fluorescent mineral display at the Santa Barbara Natural History Museum. Image on the right displays the minerals under ultraviolet light. (CC-BY 4.0; Chloe Branciforte, own work).