Exhibit 99.1

JOINT FILING AGREEMENT

The undersigned hereby agree that the foregoing statement on Schedule 13G is filed on behalf of each of the undersigned in accordance with the provisions of Rule 13d-1(k) under the Securities Exchange Act of 1934, as amended, and that all subsequent amendments to this statement on Schedule 13G may be filed on behalf of each of the undersigned without the necessity of filing additional joint filing agreements.

Date: June 17, 2020

		DICALITE MANAGEMENT GROUP, INC.
		By:	/s/ Derek Cusack
		Name:	Derek Cusack
		Title:	Vice President and Deputy General Counsel

		DICALITE MANAGEMENT HOLDINGS LLC
		By:	/s/ Derek Cusack
		Name:	Derek Cusack
		Title:	Vice President and Deputy General Counsel

		DPV MINERAL HOLDING COMPANY LLC
		By:	/s/ Matthew H. Kamens
		Name:	Matthew H. Kamens
		Title:	Manager

		MTFG MANAGEMENT SERVICES, LLC
		By:	By The Ronald O. Perelman 2016 Trust for Education and Charity, its Member /s/ Matthew H. Kamens
		Name:	Matthew H. Kamens
		Title:	Trustee

		THE RONALD O. PERELMAN 2016 TRUST FOR EDUCATION AND CHARITY
		By:	/s/ Matthew H. Kamens
		Name:	Matthew H. Kamens
		Title:	Trustee