EOSC 118 FINAL EXAM QUESTIONS
AND ANSWERS GUARANTEED PASS
2024 LATEST UPDATE
What are common treatments for corundum? - Answer- Heating to improve clarity,
diffusion treatment to add colour. Usually done before it's cut.
Can corundum be produced synthetically? - Answer- Taking the necessary oxide
components in powdered form, melting them together in a container and a seed crystal
is lowered in and slowly removed causing it to be continually grown below it.
How does corundum form in metamorphic environments? - Answer- Produces the most
significant quality. Forms best in continent-continent collisional boundaries. The rock is
a limestone that changes using high pressure to a metamorphic marble, it recrystallizes
from sedimentary bioclasts into new crystals.
How does corundum form in Alkali Basalts? - Answer- They form below the continents
in the upper mantles, taped by magmas rising to the surface, when they're entrained in
magma, they're called zenocrysts and have been found around the globe, but in
southeast Asia and Australia. Between two crusts, pushed up by magma.
Where is corundum found in placer deposits? - Answer- Weathering, settling to the base
of alluvial systems. They become rounded from their initial place, so the rounder a
stone, the farther from the beginning it is.
Why is corundum rare? - Answer- It's difficult to create the deep colours that are
produced naturally synthetically. It requires so many different things to happen for it to
go down. (Right combination of minerals in the magma etc)
How large can corundum be? - Answer- As large as 312lbs.
Where is it found locally and globally? - Answer- Globally- Sri Lanka, Kasmir, Burma,
Thailand.
Locally- Baffin Island, NFL, Quebec, BC.
, What current science is being conducted with Corundum? - Answer- Studies by Giuliani
and Tzen Fu Yui have revealed that using geocchemistry they can discover where a
stone has originated from based on the hundreds of samples they've gathered.
What are some basic tools for gemology? - Answer- Eye, tweezers, hammers.
What are some gemological tools? - Answer- Loupe- hand lens.
Chelsea filter- colour filter for red and green.
Dichroscope= Determines what class mineral or gem belongs to.
What are some mineralogical tools? - Answer- Polarizing microscope- views thin
sections of rock.
Raman microscope- outfitted with a monocromatic laser, some of the light is scattered
toward a detector, which then finds a patter that which can discern the chemical
makeup of a target.
How are pegmatites made? - Answer- Fractionation. The removal of certain minerals
due to the crystallization of those minerals. They're "fertile" if they have many elements.
If a pegmatite is fractionated, it's good because then it means that more elements are
available.
How are pegmatites classified? - Answer- Depth, range of temperature, type of rare
element enrichment.
The four groups are: Abyssal, Muscovite (Low T, High P), Rare-Element (Low T and P),
Miarolithic (Medium T, Low P)
What's the difference between simple and zoned pegmatites? - Answer- Simple-
homogenous textures, simple mineral assemblages, many crystals of small size.
Zoned-heterogenous, the kind that have a core and foster diamonds.
Why are gem bearing pegmatites rare? - Answer- They need abundant granitic rocks
and must be fertile in a rare element enrichment. Concentrations need to occur, but not
so high that a corrosive environment destroys crystals. Finally, erosion needs to remove
the overlying rock.
Where are pegmatites found? - Answer- Brazil, Madagascar, Russia, the U.S.
BC, Yukon, NWT.
What is tourmaline? - Answer- Hexagonal borosilicate mineral group that occurs in long
slender crystals with pseudo hexagonal outline and euhedral crystals. Hardness of 7-
7.5. Chemical formula- XY3Z6(BO3)3Si6O18(OH)4. Colour changes occur in the Y site
for Al. Rough- Long crystal habit.
What is Topaz? - Answer- Perfect basal cleavage, hardness of 8. Aluminosilicare
mineral containing flourine. Chemical formula- Al2SiO4(F, OH)2. Signature colour is
"Imperial" which is a reddish orange colour, caused by colour centres in the crystal with
