The secret base statues that you can find while digging for fossils in Pokémon Brilliant Diamond and Shining Pearl's Great Dungeon are extremely useful. You will place them inside your secret base and they will increase the chance that you will encounter specific types of Pokémon of the statues you place. There is also the option to acquire Shiny Statue. Here's how you can get shiny statues in Pokémon Shiny Diamond and Shiny Pearl.
Shiny statues are incredibly harder to acquire. This is because they have a low chance of falling while digging for fossils. But you can increase those chances by finding the Diglett in the Grand Underground. You may notice that one meter below your Grand Underground map on the left side of the screen goes up one by one each time you encounter a Diglett, or three times if it's a Dugtrio. This is the bonus you receive for any encounter with a shining statue, which is inside the beautiful stone boxes.
When you hit a high amount of bonuses, something around 35 points, you'll want to click the R trigger on your Nintendo Switch. A small echo-like stance will vibrate away from your character, and you'll want to do it near the fossil excavation sites you find. From there, you'll want to complete the fossil minigame as usual, and hope to find a beautiful stone box before the minigame ends.
If you are looking for these shiny statues, you also have the option of playing the Grand Underground with friends or strangers, but we recommend playing with friends so that you can coordinate with others. That way, as you explore all of the Grand Undergrounds, every Diglett and Dugtrio you find counts for everyone, making the collection process that much easier.