The first man made corundum (rubies and sapphires) were made in a laboratory in 1837; chemists Edmond Fremy and Auguste Verneuil perfected the Verneuil flame fusion process in 1877. The Verneuil ruby became very popular in the deco period for its consistency of color when using the calibrated accent rubies and sapphires. The ingredients are sprinkles in at the top and drop down onto a rotating rod inside the furnace, that slowly rotates and travels downward, forming a flat topped conical crystal called a boule. Today the main use for manmade corundum are the colorless boules that are sliced and used for scratch resistant watch crystals. The man made crystals are difficult to detect when faceted. However under strong magnification growth curves can be observed that often look like parallel curved lines on gramophones records or the end grain in wood.