Germany-based, Possehl is part of Cremer, a commodities business with annual turnover of more than €3bn.
The fledgling agreement between the two companies will see Possehl take at least 70% of commercial grade acid-spar produced at Storuman in Sweden; Lassedalen in Norway; and MB in Nevada.
Possehl will provide funds to develop the deposits and for any acquisitions Tertiary may make to bulk them up.
Tertiary will also receive logistics and infrastructure support from the German group while the projects are developed.
Possehl is headquartered in Lübeck,employs 1,800 people and shipped over 10.4mln tonnes of commodities in 2016.
The memorandum will be effective until one of Tertiary’s projects has been in production for a year or a formal offtake agreement is signed.
Richard Clemmey, Tertiary’s managing director, said he was delighted with the agreement.
“The relationship represents a critical building block in our quest to becoming a leading supplier of fluorspar to the global markets.
“Not only does this provide the company with the opportunity, and competitive advantage, to secure long-term sales contracts with key fluorspar end users but also access to pre-financing.”
Michael Fanger from Possehl added: "We have enjoyed a great working relationship with Richard over the years on various mining operations and we are excited to work with the Tertiary management team on their fluorspar operations".