Botryoidal chalcedony!

The rock in the image appears to be a type of chalcedony, possibly an agate or a similar variety. Here's why:
1. **Coloration and Banding**: The rock has a predominantly white or light gray color with some yellowish-brown inclusions. This kind of coloration and banding is typical for agates, which are a variety of chalcedony.
2. **Translucency**: Chalcedony, including agate, often has a translucent quality, which seems to be present in parts of this rock.
3. **Texture**: The rock's texture looks somewhat waxy or greasy, which is characteristic of chalcedony due to its fine-grained silica composition.
4. **Inclusions**: The yellowish-brown areas could be iron oxide or other mineral inclusions, which are common in agates and give them their varied colors. However, without specific tests like a hardness test, streak test, or chemical analysis, this identification remains speculative. For a more precise identification: - **Hardness Test**: Chalcedony has a hardness of around 7 on the Mohs scale, meaning it should scratch glass but not be scratched by a knife. - **Streak Test**: The streak of chalcedony (if it could be powdered) would typically be white or colorless. - **Microscopic Analysis**: Looking at thin sections under a microscope could reveal the mineral composition more clearly. - **Consulting a Geologist or Using Spectroscopy**: For a definitive identification, especially if this rock might be of value or scientific interest.