5 Characteristics of Minerals Remember: Now I Can DEFine mineralS. Naturally occurring Inorganic Crystalline structure DEFinite chemical composition Solid Watch: https://www.youtube.com/watch?v=-DSzlxeNCBk

Characteristics of Minerals NATURALLY OCCURRING: CRYSTALLINE STRUCTURE: Minerals occur in nature. Minerals have never been alive. A mineral is made up of specific chemicals unique to that mineral. Neither a liquid nor a gas. A mineral’s atoms are arranged in a specific pattern unique to that mineral. INORGANIC: Click animation above DEFINITE CHEM COMP: SOLID:

Elements vs. Minerals ELEMENTS MINERALS The most common elements found in Earth’s crust are oxygen, silicon, aluminum, iron, and calcium. Elements make up minerals. There are about 4000 known minerals. Only about 30 are common. The most common are quartz, feldspar, mica, and calcite.

Minerals vs. Rocks Minerals and rocks are different! Quartz, Mica, Feldspar, and Calcite make up most of the rocks found in Earth’s crust. Minerals are the building blocks of rocks. Most rocks are made of one or more minerals.

How do minerals form? 1. Crystallization from magma. 2. Precipitation, like when mineral rich water evaporates. (Example: Salt crystals) 3. Changes in pressure and temperature. 4. Hydrothermal solutions. Watch http://www.visuallearningsys.com/catalog/title/VLC151

Categories of Minerals SILICATES Most common group of minerals. Composed of Silicon and Oxygen. Make up 90% of Earth’s crust. Feldspar and Quartz are part of this group.

Categories of Minerals NATIVE ELEMENTS Native elements are minerals that are composed of a single element. Some examples are: Gold (Au), Silver (Ag), Copper (Cu), Iron (Fe), Diamonds (C), Graphite (C), and Platinum (Pt). Certain common metallic Image Courtesy of the USGS Gold Silver Image Courtesy of the USGS elements, such as iron, aluminum, and silicon are rarely, if ever, found in the native state because they are highly reactive and form compounds with other elements.

Categories of Minerals OXIDES The oxide group of minerals is composed of oxygen and a metal. Some common oxides include hematite and magnetite.

Categories of Minerals CARBONATES The carbonate group of minerals is composed of the carbonate compound CO3. Some common carbonates are calcite and dolomite.

Categories of Minerals HALIDES Halite Copyright©Stonetrust, Inc. Halides consist of halogen elements, chlorine (Cl), bromine (Br), fluorine (F), and iodine (I) forming strong ionic bonds with alkali and alkali earth elements sodium (Na), calcium (Ca) and potassium (K). Some examples include Halite (NaCl) and Fluorite (CaF2). Fluorite Image courtesy of USGS

Categories of Minerals SULFATES Barite Image Courtesy of the USGS Sulfates are minerals that include SO4 anionic groups combined with alkali earth and metal cations. Anhydrous (no water) and hydrous (water) are the two major groups of Sulfates. Barite (BaSO4) is an example of a anhydrous sulfate and Gypsum (CaSO4 · 2H2O) is an example of a sulfate. Gypsum Image Courtesy of the USGS

Categories of Minerals SULFIDES Pyrite “Fool’s Gold” Copyright©Dr. Richard Busch Sulfides are minerals composed of one or more metal cations combined with sulfur. Many sulfides are economically important ores. Pyrite (FeS2) or “fool’s gold”, Galena (PbS), Cinnabar (HgS) an Molybdenite (MoS2) are a few commonly occurring sulfide minerals. Cinnabar Image Courtesy of USGS

Identifying Minerals Remember!: Rarely is a mineral identified by a single property. These properties need to be considered together to correctly identify a mineral. To be able to identify these and other minerals, we need to look at the properties used to separate and distinguish these minerals.

Properties of Minerals Visual Properties: Color, Luster, Crystal Shape Physical Properties: Breakage, Hardness, Specific Gravity, Streak Special Properties: Effervescence, Magnetism, Fluorescence, Phosphorescence, Double Refraction

Color Color is the most easily observed mineral property and the least useful! Many minerals can have a similar color

Color Many minerals can turn colors due to impurities, or they can change colors in various circumstances. For example, pure quartz is colorless or white, impurities can make the mineral rose, purple or pink!

Luster Luster refers to the way a mineral shines in reflected light. The minerals can be described as having has a metallic luster or having a nonmetallic luster. There are several terms used to describe nonmetallic luster. Examples could be vitreous, like the quartz, or pearly, like the gypsum. Other terms that might be used include greasy, dull, and earthy. Metallic luster Nonmetallic luster Nonmetallic: Vitreous Nonmetallic: Pearly Nonmetallic: Earthy

Crystal Shape Crystal shape can be a useful property to identify minerals if the minerals have had the time and space to form crystals. Most mineral grains that are found in rocks, lack the room to grow.

Cleavage The cleavage of a mineral is its tendency to split easily or to separate along flat surfaces. Cleavage can even be observed on tiny mineral grains making it a very useful property!

Cleavage Mica is probably the best example as it splits into thin sheets. It is said to have one perfect cleavage. Feldspar splits readily in two directions, always at or near right angles. Mica Feldspar

Cleavage Calcite and galena cleave in three directions. They are said to have three good cleavages. Calcite Galena

Fracture Not all minerals show cleavage. Those that don’t break along cleavage surfaces are said to have fracture.

Hardness The hardness of a mineral is its resistance to being scratched. Diamond is the hardest of all minerals, and talc is the softest.

Hardness Friedrich Mohs devised a hardness scale. In this scale, ten well known minerals are given numbers from one to ten.

Hardness Talc (left) is the softest and has a hardness of 1. A soft pencil lead will scratch talc. Gypsum is a bit harder and has a hardness of 2. A fingernail scratches gypsum.

Hardness Calcite (left) has a hardness of 3 and a copper penny just scratches it. Fluorite has a hardness of 4 and it can be scratched by an iron or brass nail.

Hardness Apatite (left) has a hardness of 5 and can be scratched by a steel knife blade. Feldspar has a hardness of 6 and it will scratch a window glass.

Hardness Quartz (left), with a hardness of 7, is the hardest of the common minerals. It easily scratches hard glass and steel. Topaz has a hardness of 8 and will scratch quartz.

Hardness Corundum (left) has a hardness of 9. Corundum will scratch topaz. Diamond with its hardness of 10 can easily scratch the rest of the minerals.

Specific Gravity Specific gravity tells you how many times as dense as water the mineral is. Compares the density of the mineral to the density of water. Pure gold can have a specific gravity as high as 19.3!

Streak Streak of a mineral is the color of its powder when rubbed on an unglazed white tile. The streak is often not the same color as the mineral. A minerals color may vary, but the streak rarely will!

Acid Test Calcite is calcium carbonate, CaCO3. If a drop of weak hydrochloric acid is placed on calcite, the acid bubbles as carbon dioxide is released.

Other Special Properties MALLEABLE OR DUCTILE MAGNETIC Minerals that can be hammered thin or shaped are said to show these properties. Examples: Gold, Silver, Platinum Some minerals that contain Iron, are magnetic and can be picked up by a magnet. Example: Magnetite

Other Special Properties FLUORESCENCE RADIOACTIVE This is the state of glowing while under a ultraviolet light. Some minerals even glow once the light is turned off! Some minerals, such as this uraninite, are radioactive. They give off subatomic particles that will activate a Geiger counter.

Other Special Properties Salty taste Double refractions Halite (rock salt) can be identified by its taste. Some calcites, cause a double image when placed over words in a book or an object.

Mineral Resources We use minerals everyday! Talc is used in fragrances, powder, ceramics, paint. Halite is used as seasoning and food preservation. Sulfur is used in fertilizer, matches, and some antibiotics. Mica is used as an electronic insulator. Diamonds, rubies, sapphires, and other gemstones are used in jewelry. Graphite is used in pencils and for squeaky hinges. Fluorite is used as a source of fluoride in toothpaste. Bauxite is an ore mined for its aluminum. We use aluminum for cans, food wraps, airplanes, and more.

Ores Ores are rocks containing valuable minerals that can be mined or extracted. The most valuable ore deposits contain metals vital to industry and trade, like copper, gold, and iron. copper ore Gold is commonly found in quartz, however they are often not always easy to see as they are in this rock. iron ore

Gemstones A gemstone or gem (also called a precious or semi-precious stone) is a piece of attractive mineral, which when cut and polished is used to make jewelry or other decorations. Precious: Has beauty, durability, size, and rarity. (Diamond, emerald, opal, ruby, sapphire) Semi-precious: only two of those the qualities of precious gemstones. (Quartz, jade)

Where Are Gemstones Found Gems are usually found near the bottom of volcanoes or in underground caves. The volcanoes’ cooling magma allows minerals to come together. Underground caves are rich in mineral water can form gemstones from the minerals.

Mineral Resources in Virginia At one time or another, over 50 minerals have been mined in Virginia. This has contributed greatly to the state’s economy but also sometimes caused adverse impacts on the public’s health and safety, and the environment. Gold, copper, gypsum and kyanite have all been mined in Virginia.