Stromatolite Calcarenite is a type of sedimentary rock formed by the accumulation of layers of lime-rich sediments. As with any natural stone, its suitability for exterior applications in rainy climates would depend on a variety of factors.

While Stromatolite Calcarenite is generally durable and weather-resistant, it may not be the most ideal option for very rainy climates due to its inherent properties. Here are a few considerations:

1. Porosity: Calcarenite tends to be more porous compared to harder stones like granite or basalt. Porous rocks can absorb water, which may cause them to weaken over time, especially in regions with frequent or heavy rainfall. This could lead to issues like cracking or disintegration.

2. Water staining: The porosity of Stromatolite Calcarenite can also make it more prone to water staining. In rainy environments, constant exposure to moisture can result in the growth of molds, mildew, or algae on the stone surface, leading to discoloration and a less aesthetically pleasing appearance.

3. Freezing and thawing: If you live in an area with freezing temperatures, the repeated cycle of water penetrating the stone, freezing, and then thawing can further contribute to the deterioration of Stromatolite Calcarenite. The expansion and contraction caused by freezing and thawing can lead to the development of cracks or fractures in the stone.

While it might be possible to use Stromatolite Calcarenite for exterior applications in very rainy climates, it would require careful consideration, proper sealing, and maintenance. The stone should be sealed with an appropriate outdoor grade sealer to minimize water absorption and potential damage. Regular cleaning and maintenance to remove any moisture-absorbing contaminants and preventive measures to prevent water pooling or stagnation on the stone surface are also crucial.

Ultimately, consulting with a local stone supplier or a professional contractor experienced in the specific climate conditions would be advisable to determine the best stone options for exterior applications in very rainy climates.