MarketWatch takes an in-depth look at the $72 billion global polished diamond trade and finds a distinct lack of pricing clarity and a deeply flawed system that have somehow endured for decades.

IDEX reports on Wednesday Sotheby's is auctioning a 9.27-carats fancy vivid pink emerald-cut diamond at a sale that will likely attract collectors that have not seen such stones auctioned for a while. Collectors and dealers have paid top prices for exceptional diamonds at auctions in Hong Kong, repeatedly setting record prices, but offerings like the rare VVS1 clarity pink diamond carrying a pre-sale estimate price of $12.8-$19.2 million, have been scarce recently. If the gem sales at the upper end of the range it could set a new per carat record of $2 million-plus.

Vale SA will likely hand over 35% of its Simandou iron ore project to Guinea. The Wall Street Journal (sub required) is reporting that Vale, one of the top three producers of iron ore, is working on an accord whereby the company concedes 35% of the Simandou project to the Guinean government. The accord falls in line with the country' new mining laws, which allow the government to increase its stake in mining projects from 15% to 35%.

A statement put out by Ivanhoe Mines and partner Rio Tinto on Monday saying it has formally informed the Mongolian government it won't renegotiate the terms of the Oyu Tolgoi investment did not have the desired effect and the share was beaten down 6.6% on Monday. The counter’s losses began after rumours – now confirmed – surfaced that the Mongolian government is rethinking a 2009 deal that gave Ivanhoe Mines and Rio Tinto a 66% stake in Oyu Tolgoi and that it now wants half of the $6 billion gold and copper project.

The value of stock in Potash Corp. of Saskatchewan, the world’s largest miner of the soil nutrient, are down more than 13% or $6 billion since Tuesday after losing 2.8% in afternoon trade on Monday on the back of plummeting corn prices in the US. The price per bushel of the largest US crop has declined 25% since June and farmers are now hard-pressed to slash input costs which means cutting back on fertilizer. Globally there is a similar trend and in India, the world's largest importer of potash, sales were down more than 50% over the monsoon planting season.

The price of coking coal is likely to remain buoyant despite a recent price cut by Wesfarmers and softening Chinese demand for steelmaking inputs. Wesfarmers, an Australian conglomerate based in Perth, over the weekend cut the price it receives for its Curragh coal to US$280 a tonne over the next three months. The move prompted analysts to consider whether coal, like several commodities like copper, nickel, and zinc, is the next domino to fall as slowing global growth pinches commmodities.

An illegal work stoppage at La Arena Gold Oxide Mine has been resolved and mining operations have resumed, Rio Alto Mining (CVE:RIO) said on its website today.

Three mining companies in the Philippines have been raided by over 200 heavily-armed communist rebels, Forbes.com is reporting. The rebels burned heavy equipment, disarmed guards and briefly held people, according to officials.

E-mails between the State Department and TransCanada, the company behind a $7 billion proposal to build a pipeline between Canadian oilsands and Gulf Coast refineries, demonstrate "a sometimes warm and collaborative relationship," states a report in today's New York Times. The e-mails, the second batch to be released in response to a Freedom of Information Act request filed by the environmental group Friends of the Earth, show a senior State Department official at the United States Embassy in Ottawa procuring invitations to Fourth of July parties for TransCanada officials, sharing information with the company about Secretary of State Hillary Rodham Clinton’s meetings and cheering on TransCanada in its quest to gain approval of the giant pipeline, which could carry 700,000 barrels a day.