Aim: What are the properties of minerals?

What is a mineral? A mineral is a: naturally occurring, inorganic, solid that has a crystal structure and a definite chemical composition. 1. Naturally Occurring: a mineral must be formed by processes in the natural world.

What is a mineral? 2. Inorganic: a mineral CANNOT form from materials that were once part of a living thing.

What is a mineral? 3.Solid: a mineral is always solid, with a definite volume and shape. 4. Crystal Structure: the particles in a mineral must line up in a pattern that repeats over and over again.

What is a mineral? 5. Definite Chemical Composition: a mineral always contains certain elements in definite proportions. Quartz Gold

Mineral or NOT? Rock salt – AKA Halite – NaCl

Beach sand – AKA tiny pieces of Quartz – SiO 2 – Crystal shape is a pyramid Mineral or NOT?

Snow – Occurs naturally Mineral or NOT?

An ice cube Mineral or NOT?

How can we identify a mineral? Each mineral has unique properties that can be used to identify it. 1. Color: the easiest test to do on a mineral, but the least reliable.

The mineral “Quartz” comes in a variety of colors Amethyst Rose Quartz Citrine

How can we identify a mineral? 2.Streak: the color of the powdered mineral. Obtained by rubbing the unknown mineral on a streak plate (porcelain tile). Useless for white or clear minerals, or minerals harder than a streak plate.

One way to tell Fool’s Gold apart from real Gold is by their STREAK. Real gold has a golden streak Pyrite has a black or dark green streak

How can we identify a mineral? 3.Luster: how light is reflected from a mineral’s surface. – Metallic, Glassy, Pearly, Waxy, etc.

Glassy luster in Quartz Pearly luster in Muscovite Earthy luster in Hematite Metallic luster in Pyrite Metallic luster in Galena

The mineral Galena

How can we identify a mineral? 4.Hardness: a mineral’s resistance to scratching – One of the best clues in identifying a mineral

Moh’s Scale of Hardness HardnessMineralHardnessMineral 1 (softest)Talc6Orthoclase 2Gypsum7Quartz 3Calcite8Topaz 4Fluorite9Corundum 5Apatite10 (hardest)Diamond The hardness of some common items: Fingernail – 2.5 A Penny – 3.5 Glass – 5.5 A Streak Plate – 6.5

How can we identify a mineral? 5.Cleavage: the way a mineral breaks along flat, smooth planes. – What determines cleavage? The way that the crystal’s atoms lines up to form zones of weakness.

Minerals can have one, two, or several cleavage planes Mica has ONE cleavage plane Feldspar has TWO cleavage planes Halite (salt) has THREE cleavage planes

How can we identify a mineral? 6.Fracture: the way that a mineral WITHOUT cleavage breaks. Mineral has no preferred zones of weakness. Splintery fracture in Hornblende Conchoidal fracture in Quartz

Other Ways to Identify Minerals Acid – Calcite will fizz in weak hydrochloric acid (HCl) Magnetism – Magnetite will pick up paper clips / staples. Taste – Halite is rock salt and will taste salty. Fluorescence – some minerals (mostly forms of calcite) will glow in fluorescent colors under a black (UV) light. Double refraction – some clear forms of calcite will make a double image of words.

Fluorescence of Minerals

Double Refraction