Black obsidian (egg) - size M

Obsidian is a type of volcanic glass, a rock that is formed as a result of magmatic activity, when there is a rapid contact of hot acid and viscous lava with a cold environment and subsequent rapid solidification. During volcanic activity, lava is produced, which moves under the influence of gravity and applied pressures. During the journey, it is slowly cooled by radiating heat to the atmosphere, which allows crystallization. However, there may be a case where the lava comes into contact with another environment such as water. Obsidian is formed by the contact of lava with the aquatic environment. Upon touch, the lava is rapidly cooled, which leads to the formation of a glassy structure, the water begins to evaporate due to heating and is replaced by a new unheated one, which again cools other lava flows.