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Properties of Minerals. Mineral Properties we will study. Luster. Hardness. Streak. Transparency. Luster. Refers to the way light reflects from the surface of the mineral. There are two types of luster, Metallic: looks like polished metal.
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Mineral Properties we will study Luster Hardness Streak Transparency
Luster • Refers to the way light reflects from the surface of the mineral. • There are two types of luster, • Metallic: looks like polished metal. • Nonmetallic: does not look like polished metal.
Hardness • Is measured by how easy it is to scratch. • Geologists order the hardness by… • Scratched by a fingernail. • Scratched by a penny. • Scratched by a nail. • Scratched by a diamond. These are not all of the tools geologists use, but it will work for our experiments.
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.
Transparency • Transparency describes how much light is able to pass through a mineral
Streak • Red chalk on a chalk board makes red marks. White chalk makes white marks. • When some minerals are scratched along a ceramic streak plate they create different colors.
Gold • When gold is run across a streak plate it makes a yellowish-gold color.
Pyrite or “Fool’s Gold” • When pyrite is run across a streak plate, it has a black or dark green streak. • Pyrite is not worth much money, while gold is worth a lot. They look alike, so miners call it fool’s gold.
Examining the Physical Properties of Pyrite • Pyrite • Luster: When you are viewing pyrite with the naked eye, it will glisten, not shine like gold. • Hardness: Get a piece of copper and scratch the copper with the pyrite. Pyrite is harder than copper. • Scratch test: Gold will leave a pure yellow residue while pyrite will leave greenish black residue. • Edges: Pyrite has sharp edges and gold has rounder edges.
Hematite • Hematite’s color is grey, but its streak is red. • Hema means blood. • The mineral was named hematite because it looked like it was bleeding when it was taken across a streak plate.
Many minerals can be the same color. Below are gold colored minerals. Which one is gold?
The answer… None of them were real gold.