A big beautiful 2.78 ct dichroic marquise Oregon Sunstone set in sterling silver.  This stone displays 2 colors, red and green.  You can see the green at the tips and is red in the middle.  Also, depending on the angle viewed the stone may appear totally red or a blend of green and red giving it a cola color.  This big stone is suspended on a wheat chain with lobster claw closure.
 
The gemstone was mined in Oregon, USA.  Colored sunstones are far more rarer because most are almost clear to champagne colored. Dichroic is even rarer because it displays 2 colors, usually green and red.