Is there a way to find the file extension of a game asset in script?

Quick Run Down: I'm using empty GameObjects in the unity editor to act as transform.position data place-holders for instantiating(player/NPC)GameObjects during run-time via scripting. Since all these place-holders are not meant to be seen in game, I'm giving them custom unity editor gizmo icons. So I can easily see where they are visually located within the editor.

I wrote the following code to create my gizmos. The code does works as intended, but I do have an issue with it. The code allows me to drop the script on the place-holder GameObjects and then drag my gizmo texture file onto the script's inspector public texture variable. Thereby showing the custom gizmo in the editor at the place-holder's location as intended. Still, I'm not really happy with using || spawnPointIcon.name + ".png" || as my name parameter. Since spawnPointIcon.name only returns the texture's file name without the file extension. Meaning if I want to use a texture file with a different file extension then .png, I would have to hard code the extension each time. Which makes the code a tad inefficient.

So back to my actual question: Is there any possible way to find the file extension of a game asset using code? Thank you very for your time and for reading my question.

C# Code:

 using UnityEngine;
 using System.Collections;
 
 public class SpawnPointGizmo : MonoBehaviour {
     
     public Texture spawnPointIcon; 
     
     void OnDrawGizmos() {
         Gizmos.DrawIcon(transform.position, spawnPointIcon.name + ".png", true);
     }
 }