What is the general chemical formula for spinel?
Group of answer choices
MgAl2O4
Al2O3
BeAl2O4
ZrSiO4
Flag question: Question 2
Question 25 pts
How is spinel different from ruby?
Group of answer choices
Ruby does not contain Mg and has less oxyten.
Ruby is hexagonal trigonal and spinel is isometric.
Ruby has a hardness of 9 and spinel has a hardness of 8.
All of the above .
Flag question: Question 3
Question 35 pts
In what type of rock does spinel most commonly form?
Group of answer choices
metamorphic
sedimentary
basalt
shale
Flag question: Question 4
Question 45 pts
Is spinel a primary or secondary mineral?
Group of answer choices
primary
secondary
neither
both
Flag question: Question 5
Question 55 pts
Would you expect to find spinel in placer deposits? Why or why not?
Group of answer choices
No, too brittle
No, perfect cleavage leads to increasingly small crystal sizes with water transport
Yes, hardness is high, density is high
Yes, a protective coating results in good preservation
Flag question: Question 6
Question 65 pts
What crystal habit does spinel often have in the rough?
Group of answer choices
octahedrons
cubes
hexagonal bypyramids
prisms
Flag question: Question 7
Question 75 pts
What is the most common gemstone form for spinel?
Group of answer choices
faceted
cabochon
rough
tumbled in a rock tumbler.
Flag question: Question 8
Question 85 pts
What instrument or piece of equipment is useful in distinguishing ruby from spinel?
Group of answer choices
gem polariscope
refractometer
diffraction grating spectroscope
loupe
Flag question: Question 9
Question 95 pts
What property does that instrument measure?
Group of answer choices
crystal system
refractive index
absorption spectrum
large inclusions
Flag question: Question 10
Question 105 pts
What property or properties distinguishes zircon from spinel?
Group of answer choices
higher refractive index
higher density
lower hardness
all of the above
Flag question: Question 11
Question 115 pts
Which of the minerals listed in your textbook as possibly being confused with spinel have a different fluorescence?
Group of answer choices
amethyst
chrysoberyl
pyrope
tourmaline
all of the above
Flag question: Question 12
Question 125 pts
In what part of the Earth does spinel exist stably?
Group of answer choices
crust
upper mantle
lower mantle
outer core
Flag question: Question 13
Question 135 pts
What is the rock type in that part of the Earth where spinel exists stably?
Group of answer choices
peridotite
marble
syenite
basalt
Flag question: Question 14
Question 145 pts
What treatments are done to improve spinel gemstones?
Group of answer choices
irradiation
heat treatment
impregnation
color treatment
none
Flag question: Question 15
Question 155 pts
What are Balais rubies?
Group of answer choices
spinels
rubies from southeast and central Asia
synthetic spinels
imitation spinels
