1) How much effort or "mining" did it take to retrieve or process the material? If it takes a substantial amount of effort to harvast or "mine" the material, then, the material is not eco-friendly.
2) Is the item an antique? If so, it can be considered eco-friendly because you are in essense reusing the item.
3) Are the materials naturally occuring in nature (not extensively processed) or is it made from recycled synthetic materials? If the materials are naturally occuring and sourced in an environmentally sustainable way, then, it may be considered eco-friendly.
Besides the above criteria, one may also consider how the profits are used from the purchase, some individuals make purchases from companies that contribute a percent of their profits to charitable and/or eco-friendly causes.