Your question should be what is the black carbon-like thing in milk tea. Maybe it's tea leaves or black pearls.

The pearls in milk tea are rice balls made of tapioca starch. Before the powdered balls are added to milk tea, they are usually soaked in syrup to ensure that the powdered balls can still maintain their sweetness in the sweeter milk tea. The base of milk tea is usually black tea, but some stores also offer bubble milk tea that uses green tea (called pearl green milk or pearl milk green).

Generally speaking, authentic pearls on the market do not contain toxic ingredients. Moderate consumption of pearls is not harmful to the human body. However, it is not suitable for long-term consumption to avoid affecting gastrointestinal health and promoting the occurrence of obesity. The amount of edible pearls should not be too much at one time. It is recommended not to exceed 10 pearls. In addition, some vendors do not use tapioca flour to make pearls for the sake of profit, and may use gelatin and other harmful substances. Therefore, it is best to buy pearls from professional vendors. Purchase from anywhere to avoid inconvenience to your own safety.