If these crystals are white, small and evenly distributed, they are probably eggs. This shows that spinach has been damaged by some insects, but there is no need to worry too much, because this does not necessarily mean that these insects will bring serious harm. Usually, you can reduce the influence of these pests through appropriate agricultural management measures, such as strengthening the resistance of plants.
However, if these crystals are gray or black, and they seem to cover the whole leaf, then they are probably substances produced by spinach itself during its growth. This situation is often called "gray mold of spinach", which is a common fungal disease. In this case, it is suggested to strengthen the resistance of plants and maintain proper field hygiene to reduce the occurrence of diseases.
In either case, if you find that the crystals on spinach leaves do not affect eating, you can continue to enjoy spinach after washing. However, if it is suspected that the crystal of eggs has affected your appetite or health, then you may need to choose other undamaged spinach to eat.
Please note that if you are in doubt about the origin of eggs or the exact identity of spinach crystals, you'd better consult local agricultural experts or professional institutions to get more accurate information and suggestions.