What is a Mineral?

What is a mineral? Properties: Solid Cannot be a liquid or a gas Naturally Occurring Found in nature, not man-made Inorganic Is not alive and never was, non-living Fixed composition Has a chemical formula, most are formed from compounds of two or more elements, some minerals consist of one element ex. Au Crystal Form A definite structure in which atoms are arranged

What is a mineral? Definition: A mineral is a naturally formed, inorganic solid that has a definite crystalline structure.

The next few slides show an assortment of items. Questions to ask yourself when determining if an item is a mineral or not: Is it non-living material? Is it a solid? Is it formed in nature? Does it have a crystalline structure? The next few slides show an assortment of items. As a group, categorize the items as either: Minerals or Non-Minerals.

Wood

Gold

Fossil

Topaz

Bones

Granite

Quartz

Pearls

Talc

Icebergs

Diamond

Coal

Rock Salt

And the answers are… Minerals Non-Minerals Gold Topaz Quartz Talc Iceberg* Diamonds Non-Minerals Wood - once living Fossils – once living Bone - living material Granite - intrusive igneous rock Pearls – made by oysters Coal - Sedimentary rock Rock Salt – Sedimentary rock According to IMA – ice is listed as a mineral

Two Groups of Minerals Nonsilicates Silicates Do not contain combinations of Si and O May contain C, O, F, S Classes of Nonsilicates Native Elements: Au, Cu, Ag Oxides : Al or Fe combine with O Carbonates: C + O Sulfates: S + O Halides: F, Cl, I, or Br combine with Na, K, or Ca Sulfides: Pb, Fe, Ni, combine with S Silicates Contains Silicon (Si) and Oxygen (O) 90% of Earth’s crust Combine with elements such as Al, Fe, Mg, and K

Identifying Minerals Color – the same mineral can come in a variety of colors, not reliable

Luster – the way in which a mineral reflects light Metallic - opaque and reflective, like metal Submetallic - to nearly opaque and reflect well Nonmetallic - not looking like a metal at all Vitreous - glassy Silky - fibrous Resinous – yellow, dark orange, brown Waxy Pearly – like inside a mollusk Earthy – dull, looks like dirt or clay

Examples of luster:

Streak – the color of the mineral in a powdered form Cleavage – when minerals break along a smooth, flat surface Fracture – when minerals break unevenly along a curved or irregular surface

Hardness – a minerals resistance to being scratched Moh’s Scale of Hardness 1 - 10

Density – how much matter is in a given amount of space Special Properties Fluorescence – glow under ultraviolet light Chemical Reaction – fizzes with acid test Optical Properties – double image formed Magnetism – magnetic, attract iron Taste – salty Radioactivity – radium or uranium contained

Fluorescent Minerals: Some minerals fluorescence in pure samples, other require “activators” to fluorescence.

“Fizzes” with HCl acid: The chemical reaction indicates there is presence of a carbonate mineral (like calcite or dolomite)

Double Image:

Magnetism: Iron filings and nails attracted to magnetite

Follow up Questions to Mineral ID Lab: 1. Which mineral was the easiest to identify? Which trait or traits made this mineral easy to identify? 2. Which two minerals were the most difficult to tell apart? What traits did these minerals have in common? What trait or traits did you have to use to determine the names of these minerals? 3. What trait would be easiest for a field geologist to determine? Why?

4. What trait would be hardest for a field geologist to determine? Why? 5. If you were a field geologist, what tools would you want to take on a job that would require you to distinguish between fluorite, calcite, quartz, and gypsum? Why are each of these tools important?