She said residents were unaware of the company's intentions until they noticed drilling, and helicopters surveying the area.
The group lodged the petition to register an objection with the Waikato Regional Council if Sinosteel seeks resource consent.
Goodwin said the landowner was reluctant to give any information about what was going on.
He organised a meeting with the company's geophysicist, Jayson Meyer, who said up to 40 million tonnes of ironsands could be mined in the area. Meyer could not be reached for comment yesterday.
"He said the mining had completed its first stage which was the exploratory drilling. It's now in its second stage, which is a planning and feasibility study," Ms Goodwin said.
"The main thing they are after is ironsands, titanium, nickel, gold, lead and at least 10 other minerals. They explained to us that the only way to extract these minerals was via open-cast mine and that got us all alarmed."
Raglan ward councillor Clint Baddeley said he was unaware of any oversight of the activities, as drilling on private land did not require consent from the Waikato Regional Council.
But it was too early to conclude that mining would go ahead.
"The thing that has generated concern in this particular case, however, is that the way they would extract the ironsands would be by open-cast mining," Baddeley said.
"So you can appreciate the concern that we are in a rural area where the land is used primarily for the production of food."