Chatham Rock Phosphate is going to the public for the first time to raise up to $10 million, to help fund it through to the start of mining in 2015.
The fertiliser company said the public offer aims to raise $4 million with the ability to accept oversubscriptions of a further $6 million.
The offer will consist of new ordinary shares at an issue price of 35 cents per share with one option attached to every three shares issued.
The options will have an exercise price of 70 cents to receive one share.
The options can be exercised over a three month period after the grant of a marine consent for Chatham Rock Phosphate's Chatham Rise phosphorites project.
The company plans to file a final application for the marine consent next month.
It says the marine consent, together with the mining licence, expected to be granted shortly, are the key regulatory approvals needed for the project to proceed.
Until now, Chatham Rock has mainly been funded through private placements with qualified investors and annual share purchase plan offers to shareholders.