EOSC 118 EXAM QUESTIONS AND
ANSWERS ALL CORRECT
What is Spodumene? - Answer- Spodumene is a lithium (Li)-bearing aluminosilicate
mineral and is the base mineral for the gemstone varieties kunzite and hiddenite.
Spodumene is typically colourless, while light pink kunzite is uncommon and vivid green
hiddenite is considerably rare.
How is spodumene distinguished? - Answer- Spodumene forms prismatic crystals with
roughly square or rectangular outlines and two distinct cleavages that intersect at 90
degrees to one another. It has a hardness of 6.5 to 7 and a moderate specific gravity of
~3.2. Refractive indices range from 1.66 to 1.68, and commonly fluoresces under short
wave and long wave UV light. Crystals of spodumene have been mined historically for
their Li content. Specimens can reach great lengths with some up to 12.5 m. These
weigh more than 50 tonnes.
Spodumene - Answer- Spodumene is a lithium (Li)-bearing aluminosilicate mineral and
is the base mineral for the gemstone varieties kunzite and hiddenite.
What is Spodumene's Chemistry and Crystal Structure? - Answer- Spodumene has the
base formula LiAlSi2O6 with significant substitution occurring for both Al and Li. Kunzite
is the result of Mn+3 taking the place of Al and imparting the light pink colour, while the
green colour of hiddenite is due to Cr+3 replacing Al.
What Colours can Spodumene Have? - Answer- Kunzite (pink) and hiddenite (green)
are the two main gem varieties of spodumene, however, some light yellow material has
also been produced and is called triphane.
How does kunzite get its colour? - Answer- Kunzite's colour, as with morganite, is owed
to trace amounts of manganese (Mn). This gem variety is much more common than
hiddenite and is found the world over, although those originating from Minas Gerais,
Brazil and the Kabul region of Afghanistan are considered premium stones. Higher
specific gravity then Elebate.
How does hiddenite get its colour? - Answer- As with emerald, hiddenite has Cr as its
chromophore. Stunning electric green specimens have come from Hiddenite, North
Carolina, and the Kabul region of Afghanistan.
,What Does Spodumene Look Like Rough? - Answer- Spodumene often forms prismatic
crystals, which are sometimes flattened into a bladed shape. It characteristically shows
its two cleavage planes oriented 90 degrees from one another.
Which of the following are important identifiers for tourmaline in hand sample? -
Answer- Pseudo-hexagonal habit
'Vertical' striations along the c-axis of the crystal
Dichroism
Hardness (7-7.5)
Which of the following are gem varieties of spodumene? - Answer- Kunzite
Hiddenite
Elbaite
three most common organic gemstones: - Answer- pearl, amber, and coral.
The term "jade" in today's usage refers to two different and highly valued translucent
rocks: - Answer- jadeite and nephrite.
What are jadeite and nephrite prized for? - Answer- They are both prized for their high
durability and come in a wide range of colours, not just the familiar green....These two
rocks are composed of different minerals. Jadeite is comprised primarily of the mineral
jadeite (NaAlSi2O6), but is still considered a rock because there are some other
minerals contained in it as well. Nephrite is actually a mass of minerals in the amphibole
group.
Jadeite and nephrite textures: - Answer- Jadeite is often described as having a granular
texture and nephrite a silky texture, a direct result of their mineral compositions.
Similar to lapis lazuli, turquoise has been used throughout antiquity as a - Answer-
valuable carving and cabochon stone.
What element gives turquoise its characteristic colour? - Answer- copper (Cu) in its 2+
oxidation state.
Where do turquoise deposits form? - Answer- Deposits of turquoise form near the
surface close to Cu-bearing intrusive rocks as a result of surface waters percolating to
depth and interacting with these Cu-rich rocks.
Lapis lazuli: - Answer- Lapis lazuli is actually not a single mineral, but rather a mixture
comprising mostly of lazurite, pyrite, and calcite with minor diopside, sodalite and
haüyne.
. Since the gemstone, lapiz lazuli, is composed of multiple minerals, it is a .... - Answer-
rock
,Where does the blue colouration in lapiz lazuli come from? - Answer- the blue
colouration always comes from lazurite, while sodalite and haüyne are sometimes blue
in colour as well.
odalite, lazurite, and haüyne are members of the sodalite group in a category of
minerals called: - Answer- feldspathoids
he feldspathoid crystal structure: - Answer- made of linked SiO4 and AlO4 tetrahedra
with large gaps between them, which can fit larger ions like Na+, Cl-, SO42-, or the
"radical anion" S3
Amber - Answer- Amber is fossilized tree resin from conifers and some flowering trees
that date back almost 345 million years ago. Most of the amber of the Baltic region,
however, is younger at ~35 million years old while that of the Dominican Republic is ~20
million years old. This material is thought to have been used since the 13thmillennium
BC both as jewellery and later as fishing buoys due to its low density.
Exciting feature of amber: - Answer- One of the exciting features of amber is its ability to
preserve insects and material from its original growth many millions of years ago
Ammolite - Answer- -Ammolite is both a relatively "new" gemstone and one that is
produced almost exclusively from Canada.
-The gemstone ammolite is the fossil shell of an Upper Cretaceous (~70-80 million
years old) ammonite and is therefore considered an 'organic' gemstone.
In order for fossilized ammonite shell to display the vibrant colours of ammolite, the
original nacre of the ammonite's shell must be transformed to the mineral ....... (a form
of CaCO3). - Answer- aragonite
The colours we see in ammonite: - Answer- The colours we see are produced through
interference effects of light as a result of very thin layers of aragonite. Different
thickness' of aragonite lead to different degrees of interference and therefore different
colours. Thicker layers of aragonite produce interefence colours of red and green, while
thinner layers of aragonite produce interference colours of blue and violet.
The ammolite industry divides ammonite into 2 categories: - Answer- Type 1 (fractured)
and Type 2 (sheet). Type 1 is the most common and represents smaller fragments of
ammonite shell, now ammolite. The more desirable Type 2 is more rare and represents
larger portions of intact or barely fractured ammonite shells.
doublets and triplets. - Answer- composite gems with different layers (like ammolite for
example)
Pearls - Answer- Pearls are concretions - a hard mass from by the accumulation of
matter - that form inside mollusks as a defense mechanism in response to an
aggravating foreign particle.
, Pearls are commonly graded based on 5 main "S" variables: - Answer- Shape, Shade
(colour), Shine (lustre), Surface and Size
Coral - Answer- Coral is an organic gemstone that is associated with a lot of
controversy.
What type of metal deposit is turquoise typically associated with? - Answer- copper
Olivine (peridot) - Answer- Olivine itself is actually a mineral group comprising two main
solid solution end-members: forsterite (Mg2SiO4) and fayalite (Fe2SiO4). 2. The gem
variety of olivine (peridot) is almost always the mineral forsterite with a predominance of
Mg over Fe.
olivine is a major rock-forming mineral, meaning that it forms a significant fraction of
common rocks such as basalt and gabbro. It is even more significant below the crust,
where it is believed to make up the majority of the upper mantle! For this reason, the
physical properties of olivine have a major effect on plate tectonics.
alexandrite - Answer- Alexandrite is a very valuable Cr-bearing variety of the mineral
chrysoberyl, normally a light brown or golden colour. It is particularly remarkable as a
gemstone because of its colour change properties.
The garnet group - Answer- is composed of six main minerals divided into two main
mineral series: ugrandite and pyralspite. The series names are taken from the minerals
included in each group: UGRANDite for Uvarovite, GRossular, and ANDradite and
PYRALSPite for PYRope, ALmandine, and SPessartine. All of the ugrandite series
garnets contain calcium (Ca) as a major element in their structure, while those of the
pyralspite series require aluminum (Al) in their structure.
Quartz Gems - Answer- The base formula of the quartz group of gems is SiO2, but the
ubiquity of this base mineral group and the large number of variations give rise to no
less than a dozen gem varieties.
Variations in colour among diamonds are often the result of: - Answer- impurities;
deformation of the crystal, "vacancy" or hole where there would normally be an atom. It
takes very little of an impurity, site vacancy, or crystal defect to generate vivid colours in
stones.
Colourless diamonds often have: - Answer- no impurities
Blue to grey diamonds often have: - Answer- Boron impurities. Hope Diamond.
Yellow to orange, subdued to intense, as well as almost colourless diamonds often
have: - Answer- Nitrogen impuritien. Tiffany Diamond
Green diamonds often have: - Answer- Natural irradiation. The Dresden green
