Certain type of un-dissolved natural impurities (Chemical elements) which is presented in the natural rough stones (corundum’s) can be dissolved by very high heat and could improve color and open the crystal of the stones in to a transparent gem instead of semi- transparent, translucent and in some occasion translucent to opaque type of gems. 

Most Blackish Blue Sapphire are unable to change in to lighter color by heat Treatment but Sapphire with lighter color or colorless(with slight presence of un-dissolved chemical elements being in stone, such as Geuda) can be improved by heat treatment (color and clarity).

Most Sapphire rough coming out of USA mines (Montana) has no need to do pre-shaping or trimming (to remove certain type of inclusion to avoid cracking and shattering in high heat). Crystal structure formation on Montana Sapphire allows us to heat treat them as is without pre-shaping, many other origins need to be pre-shaped and trimmed (removing certain type of inclusion prior to treatment to avoid cracking & shattering ). For pre-shaping (removing certain type of inclusions), We will charge a small fee. Further your rough stones will loose some weight after pre-shaping (pre-forming)

If you’re not familiar or do not know to figure out the out come of the Heat Treatment, its advisable to Heat-Treat a small quantity like 50 carats (10 grams) to get an idea of the result of your rough stones before going on to larger quantities.