gold-melt-value 0.1.0

Compute precious-metal melt value by karat, weight, and live spot price (gold, silver).
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# gold-melt-value

[![crates.io](https://img.shields.io/crates/v/gold-melt-value.svg)](https://crates.io/crates/gold-melt-value)
[![docs.rs](https://docs.rs/gold-melt-value/badge.svg)](https://docs.rs/gold-melt-value)

Compute precious-metal **melt value** from karat (purity), weight, and a live spot
price. Pure, dependency-free Rust math — the same engine behind the
[GoldGramPrice](https://goldgramprice.com/) live gold calculator, which shows
[the price of gold per gram by karat](https://goldgramprice.com/14k-gold-price-per-gram/).

## Why

Gold is quoted per **troy ounce**, but most people hold it in **grams** and in mixed
**karats**, so the headline spot price is rarely what a given piece is worth. Melt
value = `grams × (karat/24) × (spot ÷ 31.1034768)`. This crate does that math (and
pennyweight / troy-ounce variants) with no dependencies.

## Usage

```rust
use gold_melt_value::{melt_value_grams, purity};

let spot_per_oz = 3983.30;   // USD per troy ounce
let grams = 10.0;            // a 10 g chain
let karat = 14;

let usd = melt_value_grams(grams, karat, spot_per_oz);
assert!((usd - 746.6).abs() < 0.1);
assert_eq!(purity(14), 14.0 / 24.0);
```

## Live calculator

For an interactive, always-fresh version with today's spot price built in, see the
[free gold melt-value calculator](https://goldgramprice.com/gold-calculator/) and the
[14k gold price per gram](https://goldgramprice.com/14k-gold-price-per-gram/) page.

License: MIT