Bright spot flashes like small gold flecks when viewed under an incandescent light is the mark of a cut sunstone.
This phenomena is known as Aventurescence.
This phenomena is also found in aventurine quartz, sometimes known as quartzite.
The sheen and the small spot-like flecks in sunstone and the glitter in aventurine quartz come from several reflections from a stone’s inclusion. These inclusions are usually platelets of hematite as in sunstone. In aventurine quartz, tiny inclusions of fuchsite, which is a type of mica green from the mineral chromium, produces the Aventurescence effect.
Sunstone is usually in shades of yellow or orange. The sheen in sunstone is not evenly spread, and is usually located in planes parallel to the top face of a cut gemstone. Hence, when viewing the stone, certain angles will display the sheen effect very well, while certain angles one might only find a flat bed of color.
Aventurine quartz has the resemblance of jade because of its green color. The actual body color of aventurine quartz is whitish to grey and the presence of flecks of mica give it the sparkle.
Aventurine quartz is often cut into beads and carvings.