Black Star Gravel, also known as black basalt gravel or simply black star, is derived from basalt rock. Basalt rock is a dense durable volcanic rock formed from the rapid cooling of molten lava at earth's surface. 

Basalt is known for its dark color, typically ranging from black to dark gray, and its fine grain texture. 

Basalt has a number of unique properties that make it useful for various applications. For example, its durability, strength, and resistance to wear and erosion, makes it ideal for construction and its unique color for decorative accents and features.