日之石 - Evolution Item
散發出夕陽般紅色光輝的奇妙石頭,可讓特定寶可夢進化。
Special evolution items like the 日之石 first arrived back with the second generation of Pokémon, and are now required when evolving Pokémon such as 美麗花 and 向日花怪 and 風妖精 and 裙兒小姐 and 光電傘蜥. When evolving these Pokémon, this item is required in addition to the candy, and is consumed when used.
How to get the 日之石

The 日之石 is obtained from spinning Pokestops and Gyms. There is a very low drop chance of around 1% per spin to receive a 日之石 or any of the other evolution item, and there is an equal chance of obtaining each of the 5 currently available items.
There's no way to ensure that the 日之石 will drop, but with only 4 other items, there's a greater than 50% chance that you'll receive one once you've spun over 250 Pokéstops.
The 7th day streak bonus gives you a very high chance of obtaining one of the evolution item, but it's not believed to be guaranteed.
Other evolution items
The other evolution items that can be found in Pokemon GO are: