Specific Gravity of Minerals

The familiar physical property is able to get rid of a lot of possibilities and is in many cases done right after the hardness test has been done. This test is done by weighing the weight of a mineral specimen with the weight of the same volume of water (scientifically). Since minerals have a lot different shapes to them, determining the exact volume of a specimen is almost impossible to accomplish.

Mineral luster
When minerals are looked at in reflected light they look as if they revealed a certain luster. It is quite easy to judge some types of luster, for example those that are metallic and dull. However there are other types of luster that need to be tested and it is important to learn how to differentiate them. One of the best ways you can learn to identify luster is by getting ahold of several know of mineral specimens that have all different types of luster and keep hold of them so they can serve you as samples. Remember also that the lighting is also a big factor and when testing them you will need to work in the same type of lighting. Bright lights and artificial lights can change the luster a lot. If the specimen is checked on a cloudy day, or on a day when the sun is shining, or in the shade etc, it the luster on it will look different in all the cases.

As a general rule, luster is separated into two different classifications, which are metallic and nonmetallic. The nonmetallic type has a great number of subdivisions and the testing is actually focused on this one. The following are a few of the classifications and each of them describes the example of their luster:

• Metallic: This is shiny like other metals in their natural form such as gold and silver.
• Submetallic: This is an arrangement between nonmetallic and metallic.
• Adamantine (Nonmetallic): has a bright glossy luster to it like in the case of diamonds.
• Dull (Nonmetallic): Is very dull in its appearance and can be seen in clay or chalk.
• Greasy (Nonmetallic): This has a greasy or oily surface such as in nepheline.
• Pearly (Nonmetallic): This has a silky or rayon feel to it such as can be found in abestos.
• Resinous (Nonmetallic): Is resinous such as can be found in sphalerite.
• Silk (Nonmetallic): Similar to rayon or silk such as can be found in abestos.
• Viterous (Nonmetallic): This is similar to glass such as can be found in topaz and quartz.