An oval  diamond engagement ring featuring both 18kt gold and platinum is a timeless and luxurious choice. This combination offers both durability and elegance, making the ring a stunning symbol of love and commitment.

The centerpiece of the ring would be an oval cut diamond, known for its incredible sparkle and timeless appeal. The diamond could be set in a prong setting to allow maximum light to enter and enhance its brilliance.

The band of the ring could be crafted from 18kt gold, providing a rich and warm tone that complements the diamond beautifully. The addition of platinum, known for its durability and strength, could be incorporated into the setting or as an accent to add a touch of modern sophistication.

Overall, this classic round diamond engagement ring with 18kt gold and platinum would be a breathtaking choice, combining the everlasting beauty of diamonds with the luxurious allure of both gold and platinum.