Calcite crystals will fizz when you place acid on the surface.
Minerals are naturally forming solids that are homogeneous, have a specific chemical composition and an ordered atomic arrangement. Each mineral has a unique set of physical and chemical properties that allow geologists to identify the crystal. You can perform many tests at home or in a school setting to identify the minerals crystals in your collection. Most geological tests require only household items that you can purchase at a grocery or home improvement store.
Acid Fizz Test
Crystals of calcite will effervesce, or fizz, in the presence of an acid. Calcite is a very common soft mineral that forms in many colors. Because it can look like several other minerals, the acid fizz test is useful in providing a positive identification of your sample. To perform the test you need dilute hydrochloric acid, lemon juice or vinegar. The stronger the acid, the easier you will see the fizz; however, if you are using this test with children the lemon juice or vinegar are optimal. Simply place a few drops of acid on the crystal surface. If the mineral is calcite, you will observe bubbles forming. For dilute acids, a hand magnifier will help you see the bubbles.
Fluorescent Test
Mineral crystals such as aragonite, diamond, calcite and fluorite will luminesce under an ultraviolet, or black, light. You can test your mineral crystals in a dark room. Place your samples on a table and then shine a black light on each crystal individually. If the crystal glows a new color, it is fluorescent. For example, fluorite will glow a blue color while calcite may glow in shades or red, yellow, pink or blue. The glow will disappear once the light is turned off in fluorescent minerals. Crystals that continue to glow once the black light is off are phosphorescent.
Magnetic Test
Magnetism is an important clue in the identification of a crystal. Only a few minerals such as magnetite, pyrrhotite, hematite, platinum and franklinite show strong to weak magnetism. Minerals that are magnetic will show an attraction to a magnet and will attract household items such as iron nails and paperclips. Test your minerals by holding each sample up to a magnet. Samples that show an attraction are magnetic. Alternately, you can use the sample to pick up a nail or paperclip from a tabletop.
Fracture and Cleavage Test
Minerals with cleavage will break along definite crystal plane surfaces. For example, the mineral galena has cubic cleavage and will break into smaller cubes each time it is broken. Minerals that do not have cleavage will fracture, or break unevenly. Quartz is a common mineral that fractures. Often, a swirling pattern, known as a conchoidal fracture, will appear on the surface of minerals without cleavage when the crystal breaks. However, some minerals that fracture will show splintery or uneven surfaces. To test your crystal for fracture and cleavage, gently break the sample with a hammer and observe the result. If you see flat surfaces after the break, your sample has cleavage. A swirl pattern or uneven edges are indicative of a fractured crystal.
Tags: black light, cleavage will, calcite will, cleavage will break, fluorite will, fracture will, household items
