Publicly-traded companies are regulated by securities commissions such as the U.S.'s Securities and Exchange Commission (SEC). While the U.S. has one securities commission that oversees all public companies, Canadian securities are regulated by provincial and territorial bodies such as the Ontario Securities Commission.
Public companies are required by law to submit filings such as annual reports and financial statements. It is easy to find a lot of financial information on public companies because of their filings in free, online databases such as SEDAR and EDGAR.
Canadian public mining companies are required to submit special filings to SEDAR such as the NI 43-101. Also, there are important sections to review in standard SEDAR filings that can help you with your research.
Important SEDAR filings:
The United States' Industry Guide 7: Description of Property by Issuers Engaged or to be Engaged in Significant Mining Operations outlines the SEC's mining disclosure policy:
While SEDAR and EDGAR provide free acces to Canadian and U.S. public company filings, many business databases also offer this information, but in an enhanced format. This allows you to access many filings through an easier search process and many databases provide additional supplementary information that will complement your research.