Its composition is equivalent to the basic hypabyssal rocks of gabbro. It is crystalline, fine-medium-grained, dark gray-gray-black, and usually has pyroxene structure or hypopyroxene structure. Pyroxene structure means that the average particle size of pyroxene is larger than the average length of plagioclase, which shows the phenomenon that one pyroxene wraps multiple plagioclase. If the average particle size of pyroxene is less than or close to the average length of plagioclase, pyroxene is locally wrapped with plagioclase or interlaced with plagioclase, which is called diabase structure. There are different opinions on the genesis of diabase structure and hypodiabase structure, and it is generally believed that it is formed by the early or late crystallization sequence of minerals under hypabyssal conditions. Diabase with many interstitial time or interstitial image intersections between time and orthoclase is called chronodiabase or tholeiite. Those containing zeolite, orthoclase, aegirine or aegirine are called alkaline diabase. Metamorphic pyroxene and hypersthene can occur in chronological diabase, while olivine can occur in alkaline diabase.

Diabase is often in the form of bedrock, dike, dike and sheet, and it is also filled in the crater of basalt in the form of neck or strain. The above occurrence of diabase is the main sign that distinguishes it from gabbro and basalt. Large-scale diabase intrusions, such as numerous diabase bedrock or diabase slab geological bodies, are 300 ~ 400 meters thick and often appear in the overburden with medium thickness (about 2000 ~ 3000).