Minerals

Facts about Minerals A naturally occurring homogeneous solid Minerals can be elements Minerals can be salts Minerals can be silicates The study of minerals is called mineralogy

Physical Properties of Minerals Classifying minerals can be very complicated and expensive However there are also time-effective and affordable ways There are 8 main properties that can be used to classify minerals

Crystal Structure -- This refers to the arrangement of the atoms. X-ray diffraction is used to see these arrangements. Crystal structures can range from large and granular, to layered sheets, to microscopic crystals

Hardness -- The hardness of a mineral is calculated using the Moh’s Hardness Scale. This categorizes the physical hardness of the mineral and ranges from 1 to 10. We will look at this in greater detail later

Lustre -- Refers to the way the mineral’s surface interacts to the light and can range from dull to glassy. There are three major categories of lustre: Metallic (Galena) Sub-Metallic (Hematite) Non-Metallic (Sulphur)

Colour -- What it looks like to the naked eye. Streak -- Refers to the colour of the powder a mineral leaves after rubbing it on an unglazed porcelain plate

-- Describes the way a mineral may split apart Cleavage -- Describes the way a mineral may split apart Fracture -- Describes the way a mineral breaks when broken contrary to their natural cleavage planes Specific Gravity -- This is another name for density

Moh’s Hardness Scale Devised by Friedrich Mohs Scratching tools:  fingernail (2.2) copper penny (3.5) pocket knife or common nail (5.2) piece of glass (5.5) steel file or concrete nail (7.5)

Notes for testing: Each mineral can scratch minerals with lower hardness ratings. Each mineral can scratch itself. Don’t press hard, normal scratching should do. Weathered surfaces are softer.

Corners or edges of crystals are softer. Small pieces seem softer than large pieces. When you scratch, take a close look at the scratch line - which often looks white. Is it really a scratch or is it a powder line made from the tool you used because it was softer than the item you were trying to scratch?