Like most older Native American jewelry, this piece is not stamped or hallmarked for silver content. It is sterling or a slightly lower grade of silver.
Please note that there is a slight fracture which can be seen in the top half of the top photo. The stone is completely secure in its setting. The item "GORGEOUS LARGE VINTAGE NAVAJO INDIAN SILVER MONTANA AGATE PIN BROOCH" is in sale since Friday, July 15, 2016. This item is in the category "Jewelry & Watches\Vintage & Antique Jewelry\Vintage Ethnic/Regional/Tribal\Native American (pre-1935)". The seller is "deja--voodoo" and is located in Santa Cruz, California.This item can be shipped worldwide.