The Root, Third Eye, and Etheric Chakras are supported with this combo. Agate helps stabilize the aura, eliminates/transforms negative energies, offers overall support. Lava Rock is a great grounding stone offering strength, power, courage, and stability. Hematite offers energies for self forgiveness, and counteracts spaciness/confusion. Amethyst offers spiritual protection, purification, and cleanses the aura. Stones/crystals are interchangeable terms and often the healing properties they offer somewhat overlap. Trust what you're attracted to. Your heart always leads you to what you need.
A Mala Necklace may be used for meditation and yoga practice helping one to stay focused while repeating intentions or a mantra, very personal to the wearer, on every one of the 108 stones. The Guru Stone represents the teacher(s) in your life, including you. Avoid skipping over the Guru Stone while repeating your mantra, counting only on either side of it. After 108 repetitions of your mantra, hold the GURU Stone in your closed palms and give honor and gratitude to all of the teachers in your life, including yourself. The numbers 108: 1 = the one Universe; 0 = nothing and everything; 8 = Infinity.
Bring peace of mind to yourself and to all. Namaste.