Chapter 1, 10, 12

gems and gemmology

What is gemmology

Gemology is the study of gem materials from their origins to their use in jewellery and ornamentation.

What is a gem?

A gem can be thought of as any material which is used for adornment or decoration, especially when cut and polished

What does rough mean

Any material which is in its unfashioned state. this includes beautiful crystals

what does organic mean

These are materials formed or derived from organisms. ex: amber, fossilised tree resin, pearls, which come from oysters or other shells. Also called materials of organic origin, .

The value of a gem is affected by which factors

Beauty (style of cut and shape, colour, transparency, lustre, other optical effects). Durability: hardness and toughness.

Rarity.

Desirability These factors contribute to its overall market value.

birthstone of January

Garnet

birthstone of February

Amethyst

birthstone of March

Aquamarine

birthstone of April

Diamond or Rock crystal Quartz

birthstone of May

Emerald

birthstone of June

Alexandrite, Moonstone or Pearl

birthstone of July

Ruby

birthstone of August

Peridot

birthstone of September

Sapphire

birthstone of October

Opal or Tourmaline

birthstone of November

Topaz or Citrine.

birthstone of December

Turquoise or Tanzanite

name the major cutting centres for gemstones and diamonds

India and Far East gemstones:

diamonds: India, Belgium, USA and Israel

Give the gemstone pipeline route. Name all the stages and their interactions

Mining

rough daleres - cutters - treaters

jewellery manufacturers - cutdealers

retailers

the curomer

second-hand sales and pawnbrokers

Which factors makes mining of gemstones difficult on a large scale

Gem occurrence is patchy and unpredictable, making potential difficult to assess.

Most deposits are small and found in remote, inhospitable terrain

Name 4 areas that are important for gemstone mining and which gemstones can be found in each area

Brazil: coloured stones; tourmaline, aquamarine, chrysoberyl, topaz, citrine and amethyst.

Sri Lanka: coloured stones such as sapphire, ruby, garnet, spinel, chrysoberyl, tourmaline, zircon.

Myanmar (Burma): source of fine rubies, jade and other stones.

Madagascar: geographically related to Sri Lanka: supply of gemstones, particularly for ruby, sapphires (mor ciolours topaz, garnet, zircon, chrysoberyl

What does a deposit for diamond mining need to make it profitable

100 tonnes, 25 carat = 5 grams of diamond of which 5 carats (1 gram) of gem quality

what is open-pit or open-cast mining

Open-pit or open-cast mining is a method of extracting minerals or resources from the surface by removing overburden, which involves digging a large hole in the ground. This technique is commonly used for minerals that are located close to the Earth's surface.

The ore is excavated by cutting stepped benches into the ground

At what depth becomes underground mining more economic than surface mining

300 metres

What are the forms of mining for diamonds

The main forms of mining for diamonds are alluvial mining, open-pit mining, and underground mining, each utilizing different techniques based on the location and geology of the diamond deposits.

What are the forms of underground mining for diamonds nd explain

There are different forms of underground mining for diamonds, the most common being block caving and sublevel mining. The main techniques include block caving, in which ore is left to collapse into access tunnels, and sublevel mining, which involves drilling and blasting to create sublevels for selective diamond extraction.

Block caving = a cave is excavated in the ore body above a series of access tunnels, and the overlying kimberlite is allowed to collapse in a controlled way into this cavity.

The broken ore is collected and transported via a series of tunnels for processing. Sublevel mining involves drilling and blasting to create sublevels in the ore body, allowing for the selective extraction of diamonds while minimising waste.