Valentine Diamond Engagement Ring. When you think of one special day that's all about love and celebrating the happiness that you share with another, you probably think of Valentine's Day. With that in mind, this day is the perfect one for proposing to your sweetheart. If you're in the market for an engagement ring, the option of a valentine diamond engagement ring may be one to consider. Perhaps you have discussed marriage and the importance of conserving finances or maybe you simply don't have the budget for a large ring, which is why the precious metal of gold combined with a diamond is a popular option for many couples.