Fluorite, being a relatively softer stone with a Mohs hardness of 4, is not recommended for exterior applications in very humid climates. It has a tendency to absorb water and can be prone to cracking and deterioration when exposed to moisture over a prolonged period. Additionally, fluorite is known for its vibrant color variations, which can fade when exposed to prolonged sunlight. Therefore, it is best to choose a more suitable and durable stone for exterior applications in very humid climates.