If it has any darkish green or turquoise mold on it anywhere, then don't eat it. If it's effervescent against your tongue, depending on your constitution, it might send you down the hall at a fast pace in a couple of hours.
It is good for tomatoes, as a source of calcium against blossom end rot in some tomatoes, when mixed with water and poured in one place at the
roots. When powdered milk used to be cheap we used to add that to the soil we planted tomatoes in for the calcium, but it's quite expensive now.
Mediterranean climate, hugel trenches, fabulous clay soil high in nutrients, self-watering containers with hugel layers, keyhole composting with low hugel raised beds, thick Back to Eden Wood chips mulch (distinguished from Bark chips), using as many native plants as possible....all drought tolerant.