Information regarding the average flexural strength of a specific type of onyx, such as Irans LB Perfect Peach Onyx, is not readily available or standardized. The flexural strength of a stone can vary depending on several factors, including the specific quarry, location, and variations in the material itself. To obtain accurate information on the flexural strength of Irans LB Perfect Peach Onyx, it is recommended to contact a reputable stone supplier or quarry in Iran directly. They can provide you with the specific technical data and average flexural strength of this particular type of onyx.