Solitaire Round Brilliant Diamond Engagement Ring in 18kSolitaire Round Brilliant Diamond Engagement Ring in 18k. This modern engagement ring features a . 85 carat round brilliant cut diamond that is set in 18 karat white and yellow gold. The center stone is set in a white gold basket with plenty of open space on the sides to let light in for refraction. The shoulders feature a thin line of accent diamonds that contrast well in their yellow gold setting.