The trading halt will end on the beginning of trade on Monday, May 6, 2019, or when an announcement is made to market, whichever occurs earliest.
Shares last traded at 4 cents.
The letter said: “Middle Island’s understanding of the value of Alto has clearly increased through their presence in the Sandstone Goldfield.
“Your directors believe that Middle Island now recognises the inherent value of Alto’s Sandstone Project and the 818 square kilometres of the Archean Sandstone Goldfield controlled by Alto, which your directors have long believed to be one of the most prospective gold provinces in Western Australia today.”
The board believes the offer fails to recognise Alto’s unrealised potential and that Middle Island needs Alto.
Alto’s three largest shareholders, who collectively own or control 32.12% of the company’s shares, have indicated that they do not intend to accept the offer.