It said - after theological reflection, expert input, and site visits to mine sites and communities over a one year period - NIBs have switched to a "Christian approach" to investment in the extractives industries.
It stated that it had key ethical concerns about the business conduct in extractive industries.
Its worries included management of risk, the effects of operations on communities and national economies, and operating standards.
The new policy acknowledges the positive contribution that mining can make to development.
However, it also highlights that extractives companies are particularly vulnerable to poor governance and ethical controversy, and harmful, long-lasting impacts on communities and the environment.
The new rules identifies human rights, social and economic concerns, health and safety, corruption and taxation, and environment and ecology, as ethical areas that should be considered in investments.
NIBs said it may pull out of investment companies that are unwilling or unable to uphold high standards that make the sectors more sustainable and responsible.
It said: "Disinvestment applies in cases where companies are unresponsive to investor concerns, require a disproportionate level of engagement and / or pose too great an ethical risk to warrant continued engagement."
Commenting on the policy, Loretta Minghella, First Church Estates Commissioner, who manages the Church's investments said: "This policy recognises that good economic management aligned with strong ethical standards of operation can go hand-in-hand with long term economic sustainability.
"It also provides clarity about the sorts of concerns which, left unresolved, could ultimately lead to disinvestment."
In recent years the NIBs have disinvested from two extractive companies, over ethical and corporate governance concerns
