The ratings of four Metals and Mining stocks are down this week, according to the Portfolio Grader database. Each of these rates a “D” (“sell”) or “F” overall (“strong sell”).

Banro Corp.‘s (AMEX:BAA) rating falls to a D (“sell”) this week, down from C (“hold”) the week prior. Banro Corporation is engaged in the exploration and development of four gold properties, which are known as Twangiza, Namoya, Lugushwa and Kamituga. In Portfolio Grader’s specific subcategories of Earnings Revisions, Equity, and Cash Flow, BAA also gets an F. For a full analysis of BAA stock, visit Portfolio Grader.

This week, Universal Stainless & Alloy Products‘s (NASDAQ:USAP) rating worsens to a D from the company’s C rating a week ago. Universal Stainless & Alloy Products manufactures and markets semi-finished and finished specialty steel products, including stainless steel, tool steel, and certain other alloyed steels. The stock gets F’s in Earnings Revisions and Earnings Surprise. The stock price has dropped 15.4% over the past month, worse than 1% increase the Nasdaq has seen over the same period of time. To get an in-depth look at USAP, get Portfolio Grader’s complete analysis of USAP stock.

AuRico Gold (NYSE:AUQ) ratings are on the decline this week as the company earns an F (“strong sell”). Last week, it received a D (“sell”). AuRico Gold engages in the exploration, development, and production of gold and silver projects and properties in Canada, Mexico, and Australia. The stock gets F’s in Earnings Growth, Earnings Momentum, and Earnings Revisions. Share prices fell 18.7% over the past month. For more information, get Portfolio Grader’s complete analysis of AUQ stock.

Molycorp (NYSE:MCP) is having a tough week. The company’s rating falls from a D to an F rating. Molycorp produces rare earth products, including oxides, metals, alloys and magnets for a variety of applications including clean energy technologies, technology, and defense applications. The stock gets F’s in Earnings Momentum, Earnings Revisions, and Cash Flow. Wall Street appears to agree with the stock downgrade, with share prices dropping 45.6% over the past month. As of August 6, 17.7% of outstanding Molycorp shares were held short. To get an in-depth look at MCP, get Portfolio Grader’s complete analysis of MCP stock.

Louis Navellier’s proprietary Portfolio Grader stock ranking system assesses roughly 5,000 companies every week based on a number of fundamental and quantitative measures. Stocks are given a letter grade based on their results — with A being “strong buy,” and F being “strong sell.” Explore the tool here.