This week, 12 stocks get F’s (“strong strong”) in Portfolio Grader‘s three main grading categories, Total Grade, Overall Fundamental Grade, and Quantitative Grade.

These are the worst of the worst in the entire Portfolio Grader database. This week, there are 4,198 stocks and only these 12 get failing marks in all categories to make the dreaded “Triple F” stocks list. Here they are:

Aluminum Corp. of China (NYSE:ACH) is a producer of aluminium, with operations in bauxite mining, alumina refining, primary aluminium smelting, and aluminium fabrication. It also provides ancillary products and services. Shares of the stock have fallen 28.1% since January 1. This is worse than the S&P 500, which has seen a 12.1% increase over the same period. For more information, get Portfolio Grader’s complete analysis of ACH stock.

Cliffs Natural Resources (NYSE:CLF) is an international mining and natural resources company. Since the start of the year, CLF has declined 52.3%. As of July 19, 2013, 35.8% of outstanding Cliffs Natural Resources shares were held short. For more information, get Portfolio Grader’s complete analysis of CLF stock.

Cypress Semiconductor (NASDAQ:CY) is engaged in the design, development, manufacture, and marketing of high-performance, mixed-signal, programmable solutions that provide customers with rapid time-to-market and system value. For more information, get Portfolio Grader’s complete analysis of CY stock.

Devon Energy (NYSE:DVN) explores, develops, and transports oil, gas, and natural gas liquids. For more information, get Portfolio Grader’s complete analysis of DVN stock.

Enerplus (NYSE:ERF) is an oil and gas exploration and production company that owns a large, diversified portfolio of income-generating crude oil and natural gas properties. For more information, get Portfolio Grader’s complete analysis of ERF stock.

Eagle Rock Energy (NASDAQ:EROC) engages in gathering, compressing, treating, processing, transporting, marketing, and trading natural gas, as well as fractionating and transporting natural gas liquids. Since the first of the year, EROC has dropped 10.3%. For more information, get Portfolio Grader’s complete analysis of EROC stock.

Exelixis (NASDAQ:EXEL) is a development-stage biotechnology company dedicated to the discovery and development of small-molecule therapeutics for the treatment of cancer and other serious diseases. As of July 19, 2013, 19.5% of outstanding Exelixis shares were held short. For more information, get Portfolio Grader’s complete analysis of EXEL stock.

Navistar (NYSE:NAV) manufactures and markets medium and heavy trucks, school buses, mid-range diesel engines, and service parts. As of July 19, 2013, 12.1% of outstanding Navistar shares were held short. For more information, get Portfolio Grader’s complete analysis of NAV stock.

Newfield Exploration (NYSE:NFX) is an independent oil and gas company which explores, develops, and acquires oil and natural gas properties. The price of NFX is down 4.4% since the first of the year. For more information, get Portfolio Grader’s complete analysis of NFX stock.

Swift Energy (NYSE:SFY) develops, explores, acquires and operates oil and natural gas properties, primarily those that are onshore and in the inland waters of Louisiana and Texas. Since January 1, SFY has slumped 23%. As of July 19, 2013, 16.7% of outstanding Swift Energy shares were held short. For more information, get Portfolio Grader’s complete analysis of SFY stock.

Thompson Creek Metals (NYSE:TC) is an integrated North American primary producer of molybdenum. Shares of TC have slipped 25.6% since the first of the year. As of July 19, 2013, 11.9% of outstanding Thompson Creek Metals shares were held short. For more information, get Portfolio Grader’s complete analysis of TC stock.

Walter Energy Inc. (NYSE:WLT) is a producer and exporter of metallurgical coal for the global steel industry. Shares of WLT are trading 64% lower than at the start of the year. As of July 19, 2013, 13.3% of outstanding Walter Energy Inc. shares were held short. For more information, get Portfolio Grader’s complete analysis of WLT 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.