I'm trying to create a list of bounding boxes for each cube drawn, so I can use the boxes to intersect with a ray that my mouse position is casting, but I have no idea how. I've created a list that stores the boxes, but how am I getting the values from each box?

    for (int x = 0; x < mapHeight; x++)
        {
            for (int z = 0; z < mapWidth; z++)
            {
                cubes.Add(new Vector3(x, map[x, z], z), Matrix.Identity, grass);
                boxList.Add(something here);
            }
        }


    public Cube(GraphicsDevice graphicsDevice)
  {
    device = graphicsDevice;

    var vertices = new List<VertexPositionTexture>();

    BuildFace(vertices, new Vector3(0, 0, 0), new Vector3(0, 1, 1));
    BuildFace(vertices, new Vector3(0, 0, 1), new Vector3(1, 1, 1));
    BuildFace(vertices, new Vector3(1, 0, 1), new Vector3(1, 1, 0));
    BuildFace(vertices, new Vector3(1, 0, 0), new Vector3(0, 1, 0));

    BuildFaceHorizontal(vertices, new Vector3(0, 1, 0), new Vector3(1, 1, 1));
    BuildFaceHorizontal(vertices, new Vector3(0, 0, 1), new Vector3(1, 0, 0));

    cubeVertexBuffer = new VertexBuffer(device, VertexPositionTexture.VertexDeclaration, vertices.Count, BufferUsage.WriteOnly);

    cubeVertexBuffer.SetData<VertexPositionTexture>(vertices.ToArray());


}

There aren't any clearly defined variables for the bounds of each cube created, so where do I create the bounding box from?