Rich ore ratio = [concentrate grade (%) / ore grade] (times)
=β/α=18/0.9=20
Cotton Canvas Tarps are made from 100% natural cotton canvas fabrics, so they will eventually shrink or stretch. the shrinkage will depend on the amount of exposure it gets. when constantly exposed to humidity, rain and uv rays, canvas tarps will eventually shrink. canvas tarps are not very resistant to stretching, tearing and ripping. Do not put too much tension on the grommets when securing this cover on an item. The cotton carps covered wax , these products not recommended for car or boat covers , The wax on the canvas may be wiped off .
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