Properties of minerals colour luster streak crystal

This preview shows page 11 - 12 out of 53 pages.

Properties of minerals Colour Luster Streak Crystal Structure Hardness Cleavage or Fracture Colour The most easily observed property, but usually the least useful. A mineral’s colour can be changed by the impurities that are found in the mineral. Luster The way light is reflected from a newly exposed surface. Described as either metallic or non- metallic. Some examples of minerals with non-metallic luster are calcite, quartz and feldspar. Non-metallic luster can also be described as glassy, pearly, waxy and earthy (dull). Streak The colour of the mineral in powder form. This test is done by rubbing the mineral across a white streak plate. Several minerals have a streak that is not the same colour as the mineral itself. Most metallic luster minerals have a dark coloured streak. Crystal Structure Some minerals form crystals, if there is time and room for the crystals to form. The crystal pattern of a mineral is controlled by the internal arrangement of the atoms that makeup the mineral. Some examples of this crystal structures are quartz which has a hexagonal (six sided) crystal and halite which has a cubic crystal. Page 11 of 53
Image of page 11

Subscribe to view the full document.

Engineering Geology and Soil Mechanics Hardness The ability of one mineral to scratch another. The softer mineral gets scratched. You test a mineral’s hardness by scratching the unknown mineral with an object of known hardness. Moh’s Scale of hardness is used to rate the hardness of a mineral. The chart below shows the ten minerals that makeup the hardness scale and some common materials with their hardness to test unknown minerals. One on the scale is the softest and ten is the hardest. Cleavage or Fracture If a mineral breaks along flat, smooth surfaces it shows cleavage. Cleavage can be in one, two or three directions. Some examples are 1. Mica – cleavage in one direction 2. Feldspar – cleavage in two directions 3. Calcite, Galena and Halite – cleavage in three directions Common Rock forming minerals 1. Apatite Apatite is a phosphate mineral. The name actually covers three different minerals (Fluor apatite, colour apatite and hydroxyl apatite) depending on the predominance of either fluorine, chlorine or the hydroxyl group. These ions can freely substitute in the crystal lattice and all three are usually present in every specimen, although some specimens have close to 100% in one or other. The three are usually considered together due to the difficulty in distinguishing them in hand samples using ordinary methods. Apatite is widely distributed in all rock types (igneous, sedimentary and metamorphic), but usually as small disseminated grains, or cryptocrystalline fragments. Large, well-formed crystals can be found in certain contact metamorphic rocks.
Image of page 12
You've reached the end of this preview.
  • Spring '18
  • maduranga attanayaka
  • Engineering Geology and Soil Mechanics

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern