The platinum used in platinum engagement rings is much more rare than gold and perhaps this is why it costs 4x as much as yellow gold and 2x as much as white gold. Unlike gold, platinum is used in almost its pure form in jewelry. Platinum's purity is indicated by a 3 digit number which should be marked on the band. For example, If your band is marked “950 platinum", the band is 95% pure platinum with alloys constituting 5% of the ring. Most platinum is mined in Russia and South Africa.
Platinum's silvery-white luster looks beautiful against most gemstones, hence it is increasingly a very popular choice for one's engagement ring setting. Platinum will feel heavier on one's finger than other metals.
One of the lesser known facts about platinum is that it is hypo-allergenic and will not irritate your skin. My friend, who recently got married, was complaining to me about her white-gold engagement and wedding bands, which were making her finger itch. As a result, she is only able to wear it every few days and may have to get the inside of it plated in platinum or another metal. What a hassle.
Another positive thing about platinum is that it is low maintenance. Platinum will not rust, tarnish, or require frequent trips to the jewelry repair store. My white-gold engagement ring is not making my finger itch but it lost is luster a number of months ago. When I used some self-tanner, it seemed to erode the plating revealing a yellow gold color underneath. I eventually need to take it in to get it re-rhodium-plated. In other words, I'm a low maintenance girl sportin’ a high maintenance ring.
The author just celebrated her one year anniversary and sports a beautiful ascher cut ring. She and her husband put together the website: http://www.ultimate-engagement-ring-guide.com to help you find the perfect ring.