Minerals
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What’s a mineral?
Geologists define it as any naturally occurring inorganic solid that possesses an orderly crystalline structure and crystal form and can be represented by a chemical formula.
Minerals exhibit all the following characteristics:
1-naturally occurring 2-solid substance 3- orderly crystalline structure 4- generally inorganic 5-can be represented by a chemical formula
Naturally occurring minerals can be produced by humans but not in a lab? True or false?
False. Minerals form naturally. Synthetically made ones (those produced in a lab or by humans) are not considered minerals
Minerals must be solid where?
Only crystalline substances that are solid at temperatures encountered on Earths surface are minerals
Are inorganic and organic crystalline structures both considered minerals?
Inorganic solids found in ground (naturally) are minerals. Crystalline solids (ex:sugar) found in plants for example, are not.
Quartz general formula?
SiO2 (Indicates that Quartz had 1 Si per 2 O atoms (1 to 2 ratio).) This proportion is true of any sample of Quartz. However, composition of some minerals may vary within specific well defined limits.
Diagnostic property of mineral magnetite?
Attracts a magnet
Diagnostic property of mineral halite?
Has a salty taste.
Define luster?
Appearance of light reflected from the surface of a mineral is known as luster.
Whats metallic luster?
Minerals with appearance of metals (regardless of colour) are said to have metallic luster.
Examples of minerals with submetallic luster?
Metallic minerals such as native copper and galena develop a dull coating or tarnish when exposed to the atmosphere. They’re not as shiny as samples with freshly broken surfaces.
Types of nonmetallic luster?
Vitreous (glassy) Dull/earthy (think of soil) Pearly (think of the inside of a clam shell) Silky (like silk or satin cloth) Greasy (as though coated in oil) Resinous
Types of “ability to transmit light”
Opaque Translucent Transparent
Colour as an optical property is always useful? (True/false)
False. Many minerals come In multiple colours
What’s streak? How is it obtained?
The colour of a mineral in powdered form. It is obtained by rubbing a mineral across a streak plate (a piece of unglazed porcelain)
Streak is particularly useful in distinguishing between minerals with metallic and nonmetallic luster. How?
Metallic minerals usually have a dense, dark streak. Minerals with a nonmetallic luster usually have a light streak
Do all minerals produce a streak?
No. Quartz for example being harder than porcelain doesn’t leave a streak using this method.
Crystal shape is also known as?
Habit!
Shape of well developed quartz crystals?
Hexagonal with pyramid shaped ends.
Shape of well developed garnet crystals?
12-sided.
Types of crystal shape or habit?
Bladed (flat,elongated strips) Fibrous (hair-like) Tabular (tablet shaped) Granular (aggregates of small crystals) Blocky (square) Banded (layered)
Define mineral hardness.
It’s how easy minerals break/deform under stress. This is determined by the type and strength of the chemical bonds that hold the crystals together.
Define tenacity.
Describes a minerals resistance to breaking/deforming.
Tell me about ironically and covalent lay bonded minerals.
ionically bonded minerals (ex:fluorite and halite) tend to be brittle and shatter into small pieces when struck. Minerals with metallic bonds however tend to be malleable/easily hammered into different shapes (ex: native copper)