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  1. 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; 1
  2. 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. 2
  3. 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. 3
  4. 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 4
  5. 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
  6. 6. 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
  7. 7. 7 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.
  8. 8. 8 • 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)
  9. 9. 9 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,
  10. 10. 10 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.
  11. 11. 11  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
  12. 12. 12  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
  13. 13. 13  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,
  14. 14. 14 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)
  15. 15. 15  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
  16. 16. 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. 16
  17. 17. 17
  18. 18.  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 18
  19. 19.  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. 19
  20. 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. 20
  21. 21. 21
  22. 22. 22 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.
  23. 23. 23 • 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.
  24. 24. 24 • 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.
  25. 25. 25 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.
  26. 26. 26  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.
  27. 27. 27 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
  28. 28. 28  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.
  29. 29. 29 Type and Distribution of Gemstones in Ethiopia