-
Fluorescence in More Detail
Fluorescence in minerals occurs when a specimen is illuminated with specific wavelengths of light. Ultraviolet (UV) light, x-rays, and cathode rays are the typical types of light that trigger fluorescence. These types of light have the ability to excite susceptible electrons within the atomic structure of the mineral. These excited electrons temporarily jump up to…
-
Fluorescent Minerals
What is a Fluorescent Mineral? All minerals have the ability to reflect light. That is what makes them visible to the human eye. Some minerals have an interesting physical property known as “fluorescence.” These minerals have the ability to temporarily absorb a small amount of light and an instant later release a small amount of light of…
-
Garnets as Gemstones
Garnet has been used as a gemstone for over 5000 years. It has been found in the jewelry of many Egyptian burials and was the most popular gemstone of Ancient Rome. It is a beautiful gem that is usually sold without treatment of any kind. It is also durable and common enough that it can be used in jewelry…
-
Garnet as a Geological Indicator Mineral
Although most of the garnets found at Earth’s surface have formed within the crust, some garnets are brought up from the mantle during deep-source volcanic eruptions. These eruptions entrain pieces of mantle rock known as “xenoliths” and deliver them to the surface in a structure known as a “pipe.” These xenoliths are the source of…
-
Uses of Garnet
Garnet has been used as a gemstone for thousands of years. In the past 150 years, it has seen many additional uses as an industrial mineral. The chart below shows recent industrial uses of garnet in the United States. Garnet is also used as an indicator mineral during mineral exploration and geologic assessments. Garnet as an Industrial Mineral Garnet…
-
How Does Garnet Form?
Garnet in Metamorphic Rocks Most garnet forms at convergent plate boundaries where shale is being acted upon by regional metamorphism. The heat and pressure of metamorphism breaks chemical bonds and causes minerals to recrystallize into structures that are stable under the new temperature-pressure environment. The aluminum garnet, almandine, generally forms in this environment. As these rocks are metamorphosed, the garnets start as…
-
Garnet Physical and Chemical Properties
The most commonly encountered minerals in the garnet group include almandine, pyrope, spessartine, andradite, grossular, and uvarovite. They all have a vitreous luster, a transparent-to-translucent diaphaneity, a brittle tenacity, and a lack of cleavage. They can be found as individual crystals, stream-worn pebbles, granular aggregates, and massive occurrences. Their chemical composition, specific gravity, hardness, and colors…
-
What is Garnet?
Garnet is the name used for a large group of rock-forming minerals. These minerals share a common crystal structure and a generalized chemical composition of X3Y2(SiO4)3. In that composition, “X” can be Ca, Mg, Fe2+ or Mn2+, and “Y” can be Al, Fe3+, Mn3+, V3+ or Cr3+. These minerals are found throughout the world in metamorphic, igneous, and sedimentary rocks. Most garnet found near…
-
Tripoli
Tripoli is crystalline silica of an extremely fine grain size (less than ten micrometers). Commercial tripoli is a nearly pure silica material that is used for a variety of mild abrasive purposes which include: soaps, toothpastes, metal-polishing compounds, jewelry-polishing compounds, and buffing compounds. It can be used as a polish when making tumbled stones in a rock tumbler.…
-
Quartz as a Gemstone
Quartz makes an excellent gemstone. It is hard, durable, and usually accepts a brilliant polish. Popular varieties of quartz that are widely used as gems include: amethyst, citrine, rose quartz, smoky quartz, and aventurine. Agate and jasper are also varieties of quartz with a microcrystalline structure. Special Silica Stone Uses “Silica stone” is an industrial term for materials such as quartzite, novaculite,…