The ratings of six 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’s (PAL) rating falls this week to an F (“strong sell”), down from last week’s 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.

Alumina Limited Sponsored ADR (AWC) earns an F this week, moving down from last week’s grade of D. Alumina is primarily engaged in bauxite mining and alumina refining, as well as aluminum smelting and marketing of those products. For more information, get Portfolio Grader’s complete analysis of AWC stock.

Schnitzer Steel Industries, Inc. Class A (SCHN) is having a tough week. The company’s rating falls from a D to an F. Schnitzer Steel Industries is a recycler of ferrous and nonferrous scrap metal, a recycler of used and salvaged vehicles and a manufacturer of finished steel products. In Earnings Momentum, Earnings Revisions, Cash Flow and Margin Growth the stock gets F’s. As of Jan. 13, 2014, 10.1% of outstanding Schnitzer Steel Industries, Inc. Class A shares were held short. To get an in-depth look at SCHN, get Portfolio Grader’s complete analysis of SCHN stock.

This is a rough week for Universal Stainless & Alloy Products, Inc. (USAP). The company’s rating falls to F from the previous week’s D. 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 receives F’s in Earnings Growth, Earnings Momentum and Earnings Revisions. Margin Growth and Sales Growth also get F’s. For a full analysis of USAP stock, visit Portfolio Grader.

Kaiser Aluminum Corporation’s (KALU) rating falls to a D (“sell”) this week, down from C (“hold”) the week prior. Kaiser Aluminum produces alumina, primary aluminum, and fabricated aluminum products. The stock also gets an F in Earnings Surprise. As of Jan. 13, 2014, 12.6% of outstanding Kaiser Aluminum Corporation shares were held short. For more information, get Portfolio Grader’s complete analysis of KALU stock.

This week, Keegan Resources (KGN) drops from a C to a D rating. 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 a full analysis of KGN stock, visit Portfolio Grader.

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.