1.
 What is a Gemstone?
 Which Mineral can be a Gemstone or Gem?
• Is a rarely encountered hard, durable, brilliantly
shining
and beautiful natural mineral which has high
intrinsic
value.
• In other words: rarity, durability and beauty.
• Rarity is an economic function of supply;
• Durability is a measurable physical attribute;
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2.
 Beauty is person-specific carrying
different meanings to different
individuals, and may include
properties like;
 color,
 ability to take polish,
 sheen,
 size,
 shape etc.
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3.
 Gemstones or gem materials are stones or
materials from which a gem may be cut.
 Gem includes both precious and
semiprecious stones.
 Almost all gemstones are found in stream
gravels, due to their highly resistant and
chemically inert character.
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4.
Value of Gemstones
 The 4 factors that affect the value of a gemstone
are often refered to as the "4 c's"
Colour
Clarity
Cut
Carat - 1 carat = 0.2 g, thus 5 carat = 1 g
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5.
 Gemstones are naturally formed substances and
most are minerals.
 All minerals and stones that are used to make
jewelry and ornaments are called gems.
 Gemstones such as pearls, coral and amber are
made from plants and animals.
 Gems are divided into three categories:
precious stones, semi-precious stones, and
common gemstones.
 Emeralds, rubies, sapphires and diamonds are
precious stones. 5

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Emeralds are deep green in color. They are found in
Ecuador, Peru and Columbia in South America.
Rubies and sapphires come from Myanmar (Burma),
Kashmir, Sri Lanka and Australia. Rubies are red.
Sapphires are found in cornflower blue, yellow or pink.
The finest opals are flecked with bright glints of red,
green, yellow and purple.
The richest deposits are found in Australia.
Also found in Northern Ethiopia
Today people wear rings containing their birthstones. A different gemstone
represents each month of the year. This tradition began in Poland during the
18th century 6

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EMERALD VARIETIES (BERYL)
Emerald, a variety of beryl (Be3Al2Si6O18), others are
aquamarine- differences lie mainly in color and
rarity.
Beryl occurs in granite and pegmatite, and in low-
pressure regional metamorphic rocks talc-biotite
schist near its contacts with pegmatite and other
acidic intrusions.

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• The most important sources of emerald in
the world today are in Colombia, Russia,
Brazil and Pakistan while the other varieties
are mined mainly in Madagascar, Nigeria,
India, China, Pakistan, Nigeria, Nepal and
Brazil (Mainly aquamarine and morganite)

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Uses
• These beryl gems are used only as gems, there
being no known industrial use for them at present.
 The only non-gem usage known is that of
morganite, for eye glasses
 The color of emerald is bright green – due to Cr,
 Aquamarine is bluish green, being an extension of
emerald containing greater concentration of
chromium,
 Morganite is rose colored due to presence of
lithium,
 Bixbite is red colored due to higher concentration
of lithium,

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RUTILE
Rutile, TiO2, iron oxide up to 10% is common, often
together with ilmenite (FeO, TiO2; 52.6% TiO2 and
47.4% FeO),
In heavy mineral sands, main source of titanium
metal and, to underscore this metallurgical use, it is
classified as a metallic mineral.

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 As a result, primary rutile is today found most
widespread in igneous rocks like diorite, syenite,
granite, amphibolite, etc and mostly in the form
of microscopic sizes of crystals.
 Rarely, large crystals are also encountered.
 But economically recoverable amounts occur as a
secondary mineral in heavy mineral sands.
 Australia is the leading producer of rutile

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 Commonly reddish brown in color, but sometimes,
depending on the presence of impurities, show attractive
and rich variations of violet, green, bluish and even black
colors,
 Rutile may be transparent, translucent or opaque

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 Uses
1. Titanium dioxide pigment, 2. Titanium metal, 3.
Welding rod coating,
4. Gemstone.
 The important industrial uses of titanium dioxide are:
(1) Paint, (2) Enamels and glazes, (3) Paper, rubber, textile
fabric, floor
covering, (4) Pharmaceuticals, (5) Hydrogen production,
(6) Self cleaning fabric, (7) Self-cleaning car wind screen,
(8) Chemicals,

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ORGANIC VARIETIES
Pearl
• Pearl is one of the organic gems made up of 82-88%
CaCO3 in the form of aragonite, 10-14% conchiolin (an
organic horn-like substance which holds together the
calcareous material) and 2-4% water.
• Pearls are organic materials formed biologically.
The animals that produce the pearls are of the mollusk
genera Pinctada or pearl oyster (invertebrate having a soft
unsegmented body usually enclosed in a shell)

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 Amber
Amber is not an inorganic material at all,
and it is a kind of plant fossil or
fossilized resin having comp. C40H64O4.
 It is yellow colored, sometimes light to
dark shades of red.
 Pockets of amber occur within dark blue
carbonaceous shale beds of Eocene age.
All species of Pinctada produce pearls and they live
in welldefined localities mostly the sea.
There is only one freshwater pearl known—the
mussel Unio of USA

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These synthetic opals are sometimes seen in the market, and to the
unpracticed eye may appear to be highly valuable, natural white and
black opal.
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 Why are some gems so expensive?
With the exception of diamonds, most gemstones are
highly valued Because of their :
Beauty
Rarity
Tradition
Perception of permanence
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 Occurrence of Gemstones (Geological environments)
 Igneous, metamorphic, hydrothermal and placers.
 Kimberlite and other related pipes (diamonds);
 Diamondiferous kimberlites pipes (Sapphire and pyrope);
 K-rich/Na-Li-rich pegmatites (topaz, beryl, sapphire, ruby
corundem & zircon).
 Also in basic and andesitic lava flows, and granite
intrusives.
 Metamorphic rocks generally barren, skarns contain lapis lazuli
&ruby.
 Opals -from volcanic waters, Amethyst develops in vein deposits.
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20.
Gemstones- Precious and Semiprecious
stones
• Gem includes both precious and semiprecious stones.
The most easily measurable difference between them is
hardness.
• But there are exceptions, gems softer than this value are
traded as precious stones because they fulfill many of the
other criteria (e.g., emerald, hessonite garnet, pearl, coral).
• Hardness and durability, specific gravity and favourable
density/value ratio, lustre, crystalline form, refractive index
and colors are the main physical and optical criteria for all
these gems, but in addition,
• psychological factors are of crucial importance.
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ETHIOPIA
STATUS OF GEMSTONES
• In Ethiopia, gemstones occur in Precambrian and
Phanerozoic rock assemblages and in sediments derived
from these rocks.
• Gemstones reported from Precambrian rocks include
Ruby, sapphire, garnet, beryl (aquamarine, emerald),
Tourmaline, of sub economic deposit type and many semi
precious gemstones.

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• Occur in western, southern and eastern Ethiopia
closely related to pegmatic granite rocks and
associated metavolcano-sedimentry rocks.
• Among others, the Moyle-Aroro-Yavello belt in
ONRS are known to be sub-economical and
currently mined by many Artisanal miners and co
operatives.
• Different precious minerals present in the belt includes
Beryl, chrysobrey, aquamarine, garnet, corundum (ruby,
sapphire), and quartz etc.

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• Gemstones reported from Phanerozoic
sedimentary, volcanic shield and rift related
rocks.
• They include,
Huge and numerous type of opal, agate, putrefied wood, amber,
chalcedony, Amethyst, obsidian, citrine, fluorite, jasper, and
many others.
 Among these, jasper, quartz and agate, chalcedony gem
types are located in the thick Mesozoic-Cenozoic
sedimentary (Abay, Mekele and Ogaden sedimentary basin),
and
 Peridot/ olivine, opal, besides, jasper, quartz etc in the
volcanic terrain in the central (Ethiopia high land and rift
zone) areas.

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The southern and Central Ethiopia main belts include
(1) Moyle-Mega-Yavello/MMY/ gemstone belts, and
(2) Mozozo-Wollo-Gonder gemstone belts.
• MMY Gemstone belt is underling by high grade gneissic
rocks and unique pyroclastic and dunite assemblage
covering wide area extending from Ethio-Kenya boarder to
the Arasi-Bale highlands.
• This belt shows variable gemstone varies from Beryl,
corundum, garnet and quartz groups to tourmaline, fluorite,
with minor opal, and quartz family gemstone.

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 Others such as Amazonite and others are expected in
different parts of the belts, Mozozo-Wollo-Gonder
gemstone belts/MWG belts and in central north Ethiopia
covering parts of the rift margin extending from North
Showa the Debere Berhan to north Wollo and parts of
Gonder, within the Amahara National Regional State.
 The belts have huge gemstone varieties varies from opal-
amber to agate, petrified wood and others semiprecious
gemstones, with minor variation in type and nature.

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Unique Opal-amber gemstone variety (highly
prized iridescence play of colour or the fire opal
type), is found at Mezezo in Amhara Regional
State (Debre BerhanMehal Meda) within the Menz
& Gishe, Tegulet and Bulga zones, within
the locality of Yita, Kosta Amaba, Gift, Bahir, Gift
Gaymeda, Lay Beret, Wenze Midire, Gorat and
Wedera Kables/ Wereda.
 Most Opal bearing belts are related to in welded lapilla
rhyolite-ignimbrite rocks and tuff rocks

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 Few areas, in Tigray, Southern Nation Nationality
People (SNNP) and, eastern Oromia, also show
some opal, Jasper, Chalcedony, agate, amber,
quartz, near the contact of the volcanic and
Mesozoic sediments in Hierna area and in the
Abay canyon.

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Type and Distribution of Gemstones in Ethiopia