The answer to this question is really up to you. Do your research and understand the properties, cost and practices behind the mining of the gemstone your looking to purchase.
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Moissanite and white sapphires share some similar characteristics, while others stand in contrast with one another. If you want a stone that is naturally mined but has a lower price point, white sapphires would be a good choice. If you are looking for a socially responsible gemstone that will last forever at a revolutionary value, moissanite is your best bet.