For example, glasses containing MgO where dolomite is cheaper than limestone, and low alumina glasses where feldspar or feldspathic sands are at a premium.

• 再举个例子,在白云石比石灰石廉价的地区出产的玻璃里会含MgO;在长石或长石质砂价格高涨的地区会出产低铝玻璃。