UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of the

Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): May 13, 2013 (May 8, 2013)

ALPHA NATURAL RESOURCES, INC.

(Exact name of registrant as specified in its charter)

One Alpha Place, P.O. Box 16429,

Bristol, VA 24209

(Address of principal executive offices) (Zip Code)

Registrant’s telephone number, including area code: (276) 619-4410

(Former name or former address, if changed since last report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

Supplemental Indenture and the New Convertible Senior Notes

On May 13, 2013, Alpha Natural Resources, Inc. (“Alpha”), certain of Alpha’s wholly owned domestic subsidiaries, as guarantors (collectively, the “Guarantors”), and Union Bank, N.A., as trustee, entered into a fourth supplemental indenture (the “Fourth Supplemental Indenture”) to the indenture dated June 1, 2011 (the “Base Indenture” and, together with the Fourth Supplemental Indenture, the “Indenture”) governing Alpha’s newly issued 3.75% Convertible Senior Notes due 2017 (the “Notes”).

The Notes are guaranteed on a senior unsecured basis by each of Alpha’s current and future wholly owned domestic subsidiaries that guarantee Alpha’s obligations under Alpha’s 9.75% senior notes due 2018 and will pay interest semiannually in arrears on June 15 and December 15 of each year, beginning on December 15, 2013, at a rate of 3.75% per year, and will mature on December 15, 2017.

The Notes will be convertible by the holders beginning on October 15, 2017, or earlier upon the occurrence of certain events. The Notes will be convertible at an initial conversion rate of 99.0589 shares per $1,000 principal amount of notes, equivalent to an initial conversion price of approximately $10.10 per share. The initial conversion price represents a premium of approximately 50.0% to the $7.20 per share closing price of Alpha’s common stock on the New York Stock Exchange on May 6, 2013. The conversion rate will be subject to adjustment upon certain events. Upon conversion, the notes may be settled, at Alpha’s election, in cash, shares of Alpha common stock, or a combination thereof.

Subject to earlier repurchase, holders may convert their notes at their option at any time prior to October 15, 2017 only under the following circumstances: (1) the notes will be convertible during any calendar quarter (and only during that quarter) after the calendar quarter ending June 30, 2013, if the closing sale price per share of our common stock for each of 20 or more trading days (whether or not consecutive) in a period of 30 consecutive trading days ending on the last trading day of the immediately preceding calendar quarter equals or exceeds 130% of the conversion price in effect on each applicable trading day; (2) the notes will be convertible during the five consecutive business days immediately after any five consecutive trading day period (we refer to this five consecutive trading day period as the note measurement period”) in which the trading price per $1,000 principal amount of notes for each trading day of the note measurement period was less than 98% of the conversion value of the notes on such trading day; and (3) the notes will be convertible upon the occurrence of specified corporate events. During the period from, and including, October 15, 2017 until the close of business on the business day immediately preceding December 15, 2017, holders may convert their notes at any time, regardless of the foregoing circumstances.

A holder that surrenders notes for conversion in connection with a “make-whole fundamental change,” as described in this prospectus supplement, may in certain circumstances be entitled to an increased conversion rate.

The notes are not redeemable at our option prior to maturity, and no sinking fund is provided for the notes.

Holders may require us to repurchase all or a portion of their notes upon a fundamental change, as described in this prospectus supplement, at a repurchase price in cash equal to 100% of the principal amount of the notes to be repurchased, plus any accrued and unpaid interest to, but excluding, the fundamental change repurchase date.

The Notes are Alpha’s senior unsecured obligations and rank equally with all of Alpha’s existing and future senior unsecured indebtedness. The Notes are effectively subordinated to all of Alpha’s existing and future secured indebtedness and all existing and future liabilities of Alpha’s subsidiaries, including trade payables.

This description of the Indenture and the Notes does not purport to be complete and is qualified in its entirety by reference to the Base Indenture and the Fourth Supplemental Indenture (including the form of Note), which are attached to this Current Report on Form 8-K as Exhibits 4.1 and 4.2, respectively, and are incorporated herein by reference.

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On May 8, 2013, Alpha issued a press release announcing the pricing of its underwritten public offering of $300 million aggregate principal amount of 3.75% convertible senior notes due 2017 ($345 million including the underwriters’ over-allotment option, which was exercised in full on May 8, 2013). The notes are guaranteed on a senior unsecured basis by each of Alpha’s current and future wholly owned domestic subsidiaries that guarantee Alpha’s obligations under Alpha’s 9.75% senior notes due 2018. A copy of Alpha’s press release is filed as Exhibit 99.1 hereto.

(d) Exhibits

Pursuant to the rules and regulations of the Securities and Exchange Commission, Alpha has filed certain agreements as exhibits to this Current Report on Form 8-K. These agreements may contain representations and warranties by the parties. These representations and warranties have been made solely for the benefit of the other party or parties to such agreements and (i) may have been qualified by disclosure made to such other party or parties, (ii) were made only as of the date of such agreements or such other date(s) as may be specified in such agreements and are subject to more recent developments, which may not be fully reflected in Alpha’s public disclosure, (iii) may reflect the allocation of risk among the parties to such agreements and (iv) may apply materiality standards different from what may be viewed as material to investors. Accordingly, these representations and warranties may not describe Alpha’s actual state of affairs at the date hereof and should not be relied upon.

*Filed herewith.

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SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

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Exhibit Index

*Filed herewith.

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