Mineral ID How to identify a mineral by its properties

Today you will learn Which mineral properties are most important in identification. How mineral are identified by their properties.

A mineral’s appearance helps identify it. In order to identify a mineral, you need to observe it properties – characteristics that help identify it. There are 5 main properties that we use to identify. There are many minor properties that can also help id a mineral.

Mineral Property #1 Color & Streak Color is the first thing someone notices when they view a mineral. Color is also one of the big reasons that attract people to minerals. Generally speaking, color is not a good property to be used in the identification of minerals. It is usually the first property to confuse a novice collector into making an incorrect identification. Many minerals have different colors and some minerals' colors are identical to other minerals' colors.

A mineral can be many different colors. Below is Mica.

Many minerals can be the same color. Below are gold colored minerals. Which one is gold?

The answer… None of them were real gold.

Just like with people… Outside color does not tell you much about the important characteristics.

Mineral Property #1 Color & Streak Streak is closely related to color, but is a different property because the color of the mineral may be different than the color of the streak.color Streak is actually the color of the powder of a mineral. It is called streak because the proper way to test for streak is to rub a mineral across a tile of white unglazed porcelain and to examine the color of the "streak" left behind.

Mineral Property #1 Color & Streak Pyrite (known as "Fool's Gold") is always brassy yellow when found in crystals, even broken crystals, of any size; but when powdered, produces a black streak. Gold's streak, by the way, is yellow! Hematite's streak is blood-red Galena's streak is lead gray

Mineral Property # 2 Luster A mineral’s luster is the way in which light reflects from the surface. The two major types of luster are metallic & nonmetallic. Metallic: looks like polished metal. Nonmetallic: does not look like polished metal. Nonmetallic can be shiny or dull.

Pyrite has metallic luster

Quartz has nonmetallic luster

Non

Mineral Property # 2 Luster Some other ways to describe luster are Dull - just a non-reflective surface of any kind Earthy - the look of dirt or dried mud Fibrous - the look of fibers Greasy - the look of grease Gumdrop - the look a sucked on hard candy Metallic - the look of metals Pearly - the look of a pearl Pitchy - the look of tar Resinous - the look of resins such as dried glue or chewing gum Silky - the look of silk, similar to fibrous but more compact Submetallic - a poor metallic luster, opaque but reflecting little light Vitreous - the most common luster, it simply means the look of glass Waxy - the look of wax

Quick Check Quickly answer the following: What is the first thing someone notices about a mineral? What do we call the color of the powdered mineral? Which is more reliable: streak or color?

Mineral Property # 3 How a mineral breaks When a mineral breaks it does so either by fracturing or by cleaving.fracturing Cleavage is the tendency of a mineral to break along flat surfaces. Crystal cleavage is a smooth break producing what appears to be a flat crystal face. Fracture is the tendency of a mineral to break into irregular pieces.

Cleavage Not all minerals have cleavage. Some minerals split easily along a flat surface. The number of lines that are created when a mineral is split will be the number of cleavage lines.

Mica has cleavage in one direction. It breaks along one line.

Feldspar has two lines of cleavage. It breaks along two lines.

Cleavage or Fracture?

Non

Mineral Property #4 Hardness A mineral’s hardness is its resistance to being scratched. A scale known as the Moh’s scale is often use

Non

Mohs Scale RatingType mineral What it can be scratched by… 1TalcBaby powder 2Gypsumfingernail 3Calcitebronze coin 4Fluoriteiron nail 5Apatiteglass 6Feldsparpenknife blade 7Quartzsteel knife 8Topazsandpaper 9Corundum 10Diamond

Gypsum is soft, it can be scratched by a fingernail.

Calcite is soft, but a little harder because it cannot be scratched by a fingernail, but it can be scratched by a penny.

Fluorite is harder. It can be scratched by a nail, but not a penny or fingernail.

Diamonds are the hardest mineral, so it scratches every mineral.

Mineral Property #5 Density Each mineral has a specific density. Density is the mass of a given space or in scientific terms the mass per unit of volume. For example, if you have two minerals of the same size one might be heavier than the other. The galena will be three times heavier than the same size of quartz.

Non

Mineral Property #5 Density Geologists measure density by the following: First they use a balance to determine the mass of a sample. Second, they place the mineral in water to see how much water it displaces. The volume of displace water = the volume of the sample Third they use the following formula: Density = Mass/Volume

Brain Check Try to quickly answer the following: If you break a mineral and it breaks into cubes, is it fracture or cleavage? Why? If you break a mineral with a hammer and it falls apart into a million different pieces, is it fracture or cleavage? Why? Name three things you can scratch talc with. What is the formula for density?

Some minerals have specific properties Fluorescence: some minerals glow when exposed to ultraviolet light Magnetic: Some minerals are attracted to magnets Acid: Some minerals react with acid by bubbling

SLCDFH Some Llamas Climb Down Funny Hills S Streak Powdered Color L Luster How shiny C Cleavage Breaks in sheets or blocks D Density How much mass in a given volume F Fracture Just crumbles & breaks H Hardness Can be scratched by