There are several reasons why a natural, gem-quality diamond is costly, the foremost being it's rarity. Only about 20% of all diamonds mined are gem-quality.
Also, lab-created diamonds are less costly that natural diamonds.
Industrial quality diamonds are not costly.
No, it is not (despite the LY ending). The word costly is an adjective (expensive, high-priced).
Cheap.
Dear,costly and high-priced are some of the synonyms for expensive.
Costing a lot ; expensive
costly
Since the Koh-i-Noor is not for sale, it cannot be called the most costly diamond.
Nope. Red diamond is the most expensive. There are less than 20 natural red diamonds for sale on Earth at the moment.
It's impossible to tell the largest diamond ever used in an engagement ring, but the most costly was Beyonce's at $5 Million, given to her by Jay-Z it had an 18 Carat diamond at its centre.
The costliest diamonds are gem-quality stones rated with perfect colour -- for their colour category, flawless in clarity, excellence of cut and with a heavy carat weight.
The superlative for costly is "most costly" or "costliest."
Yes, costly is an adjective. E.g. It was a costly mistake. (One that was expensive to fix, or that led to other bad consequences.)
Costly.
It should be most costly.
No Silicon is not costly. Pensil is of 3rupees in Pakistan
The opposite of costly can be cheap, inexpensive, or affordable.
The duration of Her Costly Affair is 1.6 hours.
The Chloe Diamond, weighs 84.37 carats, has a brilliant cut, a white (D color), has a topmost clarity grade of IF, and the cut, polish and symmetry were all graded excellent. It is the second most costly diamond sold at auction. You can follow the link, below, to view a photo of the stone being held between human fingers, which may give you an approximate size of the diamond. Its particular dimensions that you seek aren't readily available in a brief search.