Contract Source Code:

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

contract GemToken {
    string public name = "Gem";
    string public symbol = "GEM";
    uint8 public decimals = 18;
    uint256 public totalSupply;
    address public owner;

    mapping(address => uint256) private balances;
    mapping(address => mapping(address => uint256)) private allowances;

    // Events
    event Transfer(address indexed from, address indexed to, uint256 value);
    event Approval(address indexed owner, address indexed spender, uint256 value);
    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

    // Constructor to set the initial supply and assign ownership
    constructor(uint256 initialSupply) {
        owner = msg.sender;
        totalSupply = initialSupply * (10 ** decimals);
        balances[msg.sender] = totalSupply;

        emit Transfer(address(0), msg.sender, totalSupply);
    }

    // Modifier to restrict functions to the owner
    modifier onlyOwner() {
        require(msg.sender == owner, "Not the contract owner");
        _;
    }

    // Transfer ownership
    function transferOwnership(address newOwner) external onlyOwner {
        require(newOwner != address(0), "New owner cannot be the zero address");
        emit OwnershipTransferred(owner, newOwner);
        owner = newOwner;
    }

    // Check balance of a specific address
    function balanceOf(address account) external view returns (uint256) {
        return balances[account];
    }

    // Transfer tokens to a specific address
    function transfer(address to, uint256 amount) external returns (bool) {
        require(to != address(0), "Cannot transfer to the zero address");
        require(balances[msg.sender] >= amount, "Insufficient balance");

        balances[msg.sender] -= amount;
        balances[to] += amount;

        emit Transfer(msg.sender, to, amount);
        return true;
    }

    // Approve an address to spend tokens on behalf of the caller
    function approve(address spender, uint256 amount) external returns (bool) {
        require(spender != address(0), "Cannot approve the zero address");

        allowances[msg.sender][spender] = amount;
        emit Approval(msg.sender, spender, amount);
        return true;
    }

    // Check the allowance of a spender for a specific owner
    function allowance(address ownerAddress, address spender) external view returns (uint256) {
        return allowances[ownerAddress][spender];
    }

    // Transfer tokens from one address to another using allowance
    function transferFrom(address from, address to, uint256 amount) external returns (bool) {
        require(to != address(0), "Cannot transfer to the zero address");
        require(balances[from] >= amount, "Insufficient balance");
        require(allowances[from][msg.sender] >= amount, "Allowance exceeded");

        balances[from] -= amount;
        allowances[from][msg.sender] -= amount;
        balances[to] += amount;

        emit Transfer(from, to, amount);
        return true;
    }

    // Mint new tokens (only callable by the owner)
    function mint(address to, uint256 amount) external onlyOwner {
        require(to != address(0), "Cannot mint to the zero address");

        totalSupply += amount;
        balances[to] += amount;

        emit Transfer(address(0), to, amount);
    }

    // Burn tokens (only callable by the owner)
    function burn(address from, uint256 amount) external onlyOwner {
        require(balances[from] >= amount, "Insufficient balance to burn");

        totalSupply -= amount;
        balances[from] -= amount;

        emit Transfer(from, address(0), amount);
    }
}