Lecture 8 Flashcards
What can the physical properties of minerals be used for?
Description and recognition of minerals in the field (but not entirely sufficient)
What do the physical properties of minerals depend on?
Mineral chemistry (composition and nature of bonds)
What are some of the physical properties taken into consideration in mineral classification?
Colour, cleavage/fracture, lustre, crystal faces and form, habit, alteration, hardness, twinning
How can colour be a deceiving property?
When pure, some minerals always present the same colour. However, impurities can change the colour of the mineral (ex: pure fluorite is clear, but can be green, purple, red, yellow, black)
What does hardness refer to?
Force required to scratch the mineral surface.
Are hard minerals the toughest?
Not necessarily. Toughness refers to trying to smash it.
What is the hardest mineral and the softest?
Hardest: Diamond (10)-scratches everything
Softest: Talc (1)-scratches nothing
What is the Moh’s Hardness Scale?
Relative scale that helps categorize mineral hardness (scratching)
What is lustre?
Qualitative expression of light reflection from a mineral
What are the most common descriptive terms of lustre?
Vitreous, silky, dull, greasy
What is the best way to look at the crystal faces and form of a mineral?
Thin sections so light can pass through it
What is a Euhedral crystal shape and form?
Well defined shape, flat faces, sharp corners. Minerals have true form
What is a subhedral crystal shape and form?
Elongated. Faces are not flat, rounded corners. Not well defined
What is an Anhedral crystal shape and form?
2 types, no regular shape.
How does the crystal shape and form come about?
As molten matter moves to the surface, crystallization begins. Ions and atoms move together to create centres of nucleation and crystal structures begin to form. As they move closer to the surface, centres of crystallization grow more.
Which mineral shape is the first to crystallize?
Euhedral-lots of room to grow
Which mineral shape is the second to crystalize?
Subhedral-not as much strength to create corners and faces, lower temp
Which mineral shape is the last to crystallize?
Anhedral-lowest temperature, no strength to grow
What mineral is the most frequent mineral on earth?
Olivine (dominant in the MANTLE)
What are transparent minerals?
Objects can be seen through them (allows light to pass through in thin sections)
What are translucent minerals?
Objects cannot be clearly seen (light can pass through in thin sections)
What are opaque minerals?
Objects cannot be seen through them (light will never pass through)
