What kind of seed is this?

Based on the information you provided, this seed could come from a variety of plants. Here are some possibilities:

1. Pine nuts: Pine nuts, also known as pine nuts, fruit pine nuts, and sea pine nuts, are the seeds of Pinaceae plants such as Korean pine, and are one of the common nuts. It is rich in fat, protein, carbohydrates, etc., and is an important traditional Chinese medicine. It can keep the mind healthy, moisturize the skin, and prolong life. It also has high therapeutic value. In China, there are Brazilian pine nuts, Northeastern pine nuts and fallen pine nuts. Among them, fallen pine nuts are mainly pine nuts from pine trees in the mountains of Yunnan, Guizhou and Sichuan.

2. Cherry pit: Cherry pit, also known as cherry seed. Cherry is a perennial woody plant of the genus Prunus in the Rosaceae family. The bark is gray-white, the branches are gray-brown or gray-brown, and the twigs are green; the leaves are oval; the inflorescence is umbrella-shaped, and the petals are obovate, white or pink; the fruit is nearly spherical, It turns red when mature; the flowering period is from March to April; the fruiting period is from May to June.

If none of the above possibilities are certain, then the seed may have come from another plant. It is recommended to consult a professional for more accurate information.