So take a light source like a phone or a flashlight and put your stone in front of it. If the stone is opaque, it does not allow light to travel through it. If it is translucent light will pass through, lighting the stone up. Your stone is not an agate. For the neophite, an agate will most likely be translucent. Agates and quartz and chalcedony are all different versions of SiO2. They are silicates and are very hard. Normally these rocks do not crack. They will chip out fragments which are called conchoidal fractures. The same type of fractures you would see used by North American peoples to make tools and knives. That would be true for indigenous people everywhere. Also the silicates can be divided by crystal structure. Quartz has big crystals or it can be called macrocrstalline. You can see the crystals with your unaideid eye. You can feel them by running your hand over it. With agate and chalcedony you have microcrystalline structure. If you run your fingernail it will not catch on the crystals. You cannot see them with the naked eye. Rocks from the microcrystalline silicas will fell slightly waxy and very smooth. There will be no cracks in them but there will be conchoidal fractures. Silicas are the most abundant materials on earth. They are formed in everyway rocks can form. The many different forms of silica include quartz, agate, flint, chert, chalcedony. Your rock looks like maybe rosy quartz. If you can scratch it with a nail file it is a different type of rock.