The ratings of three 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”).

North American Palladium (PAL) ratings are on the decline this week as the company earns an F (“strong sell”). Last week, it received a D (“sell”). North American Palladium is a mineral exploration and production company. In Portfolio Grader’s specific subcategories of Earnings Revisions, Equity and Cash Flow, PAL also gets an F. To get an in-depth look at PAL, get Portfolio Grader’s complete analysis of PAL stock.

Olympic Steel, Inc.’s (ZEUS) rating falls to a D (“sell”) this week, down from C (“hold”) the week prior. Olympic Steel processes and distributes flat-rolled carbon, stainless steel, and tubular steel products. The stock gets F’s in Earnings Surprise, Margin Growth and Sales Growth. For a full analysis of ZEUS stock, visit Portfolio Grader.

Slipping from a C to a D rating, Keegan Resources (KGN) takes a hit this week. Keegan Resources, a junior gold company, engages in the exploration and development of gold properties in Ghana, west Africa. The stock gets F’s in Equity and Cash Flow. For more information, get Portfolio Grader’s complete analysis of KGN 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.