Vermiculite is a naturally occurring mineral that expands when heated. It is often used in gardening and construction due to its lightweight and insulating properties. When heated, vermiculite can increase in size up to 15 times, creating small, accordion-like particles that are excellent for retaining moisture and improving soil aeration. In gardening, vermiculite is commonly mixed with soil to enhance drainage and provide a better environment for plant roots. In construction, it serves as an insulating material in walls and ceilings, helping to regulate temperature and reduce energy costs.