I do not have the expertise to provide a definitive answer on this subject. However, based on the available information about felsite, it is not recommended for use in exterior applications in very sunny climates. Felsite is a type of volcanic rock that is highly porous and prone to weathering, erosion, and discoloration when exposed to harsh weather conditions, including sunlight, rain, and extreme temperatures. It may also react with chemicals in the air and water, leading to further degradation. Therefore, it is advisable to use more durable and weather-resistant materials, such as concrete or natural stone, for exterior applications in sunny climates. It is always best to consult with a professional architect or contractor for specific recommendations on materials for your particular project.