Native American Navajo Silver and Turquoise Brooch/Pin measures approx 2.5" x 1.25".  The stone is probably rare Dry Creek turquoise. 

Also known as "White Turquoise"or "Sacred Buffalo Turquoise", Dry Creek Turquoise has a characteristic white or very pale blue color with brown flecks in it almost like confetti. Because white turquoise is as rare as the white buffalo, it is sometimes referred to as Sacred Buffalo Turquoise. White turquoise was found in the Dry Creek Mine near Battle Mountain, Nevada. The mine is closed. This stone is very rare and collectible.

When discovered in the Dry Creek Mine (Note: not it's name today) in the Shoshone Indian Reservation near Battle Mountain, Nevada in 1993, they (the discoverers) were not sure what it was. Because of its hardness, it was decided to have it assayed. Their suspicions proved correct. It was, in fact, white turquoise.