Emerald crystals and a loupe on dark slate

Independent iOS Developer

Sergio Montalban

I build precise, offline-first tools for people who work with their hands and expect their software to be as exact as their instruments.

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Portfolio

A small catalogue, kept deliberately small. Each app is maintained by hand.

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Obsidian Codex

iOS

A working bench for identifying stones

Test sheets, a specific gravity calculator, a hardness board, a collection drawer and an index of gem families — the notebook and reference table that sit next to your loupe.

iPhoneiPadOffline-first
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Working on something?

Feature requests, bug reports and collaboration enquiries all reach me directly.

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