Mineral properties flowchart

MINERALS – Laboratory 2 __________________________ (Name) Learning Outcomes: A. Students will be able to identify 19 different minerals based on their mineral properties. B. Students will be able to define the following terms; luster, color, streak, hardness cleavage, and habit. This lab is modified, with permission, from the one created by Gary Jacobson of Grossmont Community College. INTRODUCTION In this lab you will learn how to identify about 19 different minerals. Correct identification requires knowing the properties of each mineral and determining them accurately. It is not enough to know how each mineral “looks”, for the same mineral can look differently in different specimens. Likewise, two different minerals can look the same. Properties are more reliable. Each mineral has a unique set of properties that do not vary from specimen to specimen. The methods we will use to identifying our minerals are restricted those that can be performed in the field. This limits the kind tools we can use and it also limits our ability to determine properties. Most specimens will only permit accurate determination of a few properties, but that’s usually enough to make a reasonably certain identification. The trick lies in knowing what particular properties to determine and how to do that correctly. PHYSICAL PROPERTIES Below are listed the mineral properties that can generally be determined in the field. They are listed in roughly the order in which they are determined. Not all these properties apply to, or are important for, each mineral. Luster, Color and Streak When light is applied to a mineral it is either absorbed or reflected. We only see what is reflected. Reflection occurs on the surface of the mineral, and if the mineral is translucent, it may also occur on internal surfaces (i.e. fractures or cleavages) as well as from internal atoms. LUSTER refers to the directional and spatial qualities of the reflected light. Smooth surfaces reflect light in orderly directions – like a mirror, and produce a vitreous (glassy) luster. Irregular surfaces scatter the light in random directions and produce a dull or earthy luster. The interaction of light reflected from internal surfaces can produce more exotic lusters like pearly, resinous, or adamantine (brilliant) lusters. Luster can also be defined as metallic – looks like metal (silvery, bronzy, gold). Later we will refer to minerals as being non-metallic, meaning the mineral has a luster other then metallic. COLOR is determined by the wavelength and intensity of the reflected light. “White” light contains all the wavelengths detectable by the human eye. The more white light reflects off the surface of the mineral the lighter the mineral will be. Aggregates of small crystals will therefore be generally lighter than those of larger crystals because there are more surfaces to reflect from. Larger crystals will tend to absorb more light and thus appear darker. Trace impurities in the mineral can greatly influence both the quantity and quality of light absorption and reflection. Use great discretion when evaluating color. STREAK is the color of the powdered mineral. Since color depends on crystal size and aggregation, powdering standardizes these properties and produces a more reliable indication of a minerals true color. An easy way to powder a mineral is to drag it across the rough surface of an unglazed tile (streak plate). Hardness HARDNESS refers to a mineral’s ability to resist scratching relative to the ten minerals on Moh’s scale of hardness (Figure 1.1). To determine a mineral’s hardness, rub it against a substance of known hardness and see which is scratched. Although straightforward, the scratch test can be misleading. If care is not taken with aggregates (masses of intergrown crystals), weathered and/or easily cleaved specimens, the test may indicate properties that have nothing to do with hardness. One such property is toughness – a mineral’s resistance to breaking. Diamond is the hardest mineral, but jade is the toughest. Kits containing the ten minerals of Moh’s scale are available but generally not used because geologists like to keep field gear to a minimum. Instead most geologists sacrifice precision for simplicity, and prefer to judge hardness relative to substances that are almost always at hand – like a fingernail (H~2.5) and a knife blade or glass (H~5.5). Determining a combination of diagnostic properties for the mineral usually compensates for lack of precision in hardness testing. Figure1.1 – Moh’s hardness SCALE Cleavage The orderly arrangement of atoms within a crystal can create parallel planes of weakness along which a mineral tends to break. The most common cleavage types are shown below: Figure 1.2 - BASAL CLEAVAGE - One direction parallels to the top and base. Figure 1.3 – PRISMATIC CLEAVAGE – Two directions @ ~90o. Figure 1.4 PRISMATIC CLEAVAGE – Two directions @ ~ 57o and 123o. Figure 1.6 RHOMBOHEDRAL CLEAVAGE Three directions parallel to the sides of a rhombohedron. Figure 1.5 CUBIC CLEAVAGE - Three directions @ 90o.
1.) Download the Mineral Box Handbook to view different types of minerals. This is a large file so be aware that it may take up to several minutes to complete the download.

2.) Download the Lab 2 - Minerals Lab Packet and answer all questions.

http://www.spaceman.ca/mineral/index.php you will use this source of information to complete the table