Greensand (glauconite) is a mineral mined in New Jersey. It's rich in potassium and also contains magnesium, iron and silica. Potassium does not move through the soil as does nitrogen so does not leach out of the soil and needs biological activity to activate it. Greensand is also said to loosen heavy clay soils and improve the moisture retention of sandy soil. The recommended method is to broadcast 50 to 100 lbs. per 1,000 square feet. It improves plant health in general and is also used to loosen heavy, clay soils. It will also improve the moisture retention of sandy soils. Greensand is OMRI listed for organic use. Use according to package directions. Without a soil test,I could add it to the soil in your veg garden now, but I would get a soil test before making it a yearly application.
Azomite is also a mined mineral (Utah). It is said to be beneficial to plants and animals alike. My best suggestion is to plant some of your garlic with and without and see if you see a difference.
These minerals need a healthy soil web to break them down and make them available to the plants. Compost and organic mulch over the winter will help the mix. Best and Happy Yardening, Nancy