Saturday, 22 June 2013

A Little Insite into what Diamonds are and how its Formed...



What is a Diamond?

Madhuri Sarvothama
Diamond Grading and Gemology Instructor, SDI


Diamond is a mineral that is a crystalline form of carbon (latin: Carbo"Coal"). Like graphite, diamond's chemical composition is Carbon. The carbon atoms in diamond are arranged in tight three- dimensional patterns with strong bonds in all direction, which makes diamond the hardest natural substance and an ideal gem for everyday wear.

Diamond- Round Brilliant Cut


Different views of a Round Brilliant Cut

How are Diamonds Formed?

Diamonds form between 90 and 120 miles under the surface of the earth, deep beneath the continents. This is where ideal conditions for normal diamond formation can exist- a temperature range of 900 degrees Celsius to 1300 degrees Celsius and pressures between 45 to 60 kilobars more than the normal sea- level pressure. Diamonds form three in two types rocks called peridotite and eclogite. They may remain below the earth for billions of years until conditions within the earth's mantle and magma rapidly transports the already- formed diamonds from the mantle region to the surface of the earth, leaving carrot- shaped pipes. Then the diamonds that are not blasted onto the surface may stay in the pipes for millions of years before someone discovers them. the host rock of the diamonds in the pipe is Kimberlite or Lamproite.

Diamond in the Ore


               If the diamonds are found in and around the pipes then this kind of deposits are called primary deposits. And all other deposits are called secondary deposits. If  due to weathering conditions, diamonds were carried into neighboring rivers and streams, and even into the ocean. Since diamonds are heavy, they sink to the bottom when caught in small whirlpools. Deposits in rivers and streams are called alluvial deposits and often contain higher quality diamonds than primary deposits within a diamond pipe because the better ones are more likely to survive the water's tumbling action against rocks. If the diamonds reach the ocean, they are called marine deposits.        
                

Bibliography:
RenĂ©e Newman, Diamond Handbook- a practical guide to diamond evaluation: completely  revised 2nd edition