Why is this the answer?

The answer is ice because this is a wonderful riddle that uses word pictures to describe frozen water. Let's look at the four clever clues one by one to see how they all fit together. The first clue says that the object is A precious stone, as clear as diamond. If you hold up a piece of ice, like an icicle or an ice cube, it is perfectly clear and catches the light, making it sparkle just like a real gem or a diamond. This is a beautiful way to describe the appearance of solid water. The second part tells you to Seek it out while the sun's near the horizon. This means you often find it when the sun is just coming up in the morning or just setting in the evening. Why? Because these are the times of the day when the air is coldest, which is exactly what water needs to freeze. The sun being low tells you it's the chilly part of the day, making it the perfect time to find this stone. The third clue is really amazing: Though you can walk on water with its power. We all know that you can’t walk across a swimming pool or a lake. However, when the temperature drops, that water turns into a solid sheet of ice. This strong, frozen water lets you stand, walk, skate, and even play games right on top of it. It’s like ice gives you a special superpower to walk where you couldn't before. The last and final clue confirms the answer perfectly: try to keep it, and it'll vanish in an hour. Ice is not permanent. If you try to hold a piece of ice in your hand or keep it on the counter, your warmth and the air’s warmth will quickly turn it back into liquid water. It will melt and disappear from your hands in a short amount of time, proving that ice is the only thing that fits every single one of these tricky and clever clues.