Privacy Policy for Mineral Signal
Last updated: September 10, 2026
Mineral Signal is a crystal and mineral identification and reference app. This Privacy Policy explains what information is processed when you use the app, why it is processed, and which third-party services are involved.
1. Anonymous account
Mineral Signal creates an anonymous account when you first use the app.
This account is identified by a randomly generated identifier (UUID). We do not require your name, email address, password, or other direct personal information to use the app.
A session token is stored securely in the iOS Keychain on your device. Our server stores only a cryptographic hash of that token.
The anonymous account is used to:
- authenticate requests to Mineral Signal
- manage scan credits
- process subscriptions and Scan Pack purchases
- support Restore Purchases
- keep scan and entitlement records consistent
2. Photos used for AI scans
When you use AI Scan Mode, Mineral Signal sends the photos you select or take to our server so that the specimen can be analysed.
A scan normally includes two or three JPEG images together with technical scan information such as:
- a scan request identifier
- the selected surface description
- optional observations entered during the scan process
The images are processed on our server and are then sent to OpenAI for AI-based mineral and crystal identification.
Your Mineral Signal account identifier and authentication token are not included in the image payload sent to OpenAI.
In the production system, scan images are processed in memory and are not stored as image files in our database.
We do store:
- a cryptographic fingerprint of the processed images
- scan identifiers
- the identification result returned by the scan
- information required to operate and troubleshoot the scan service
Mineral Signal may temporarily keep scan images on your device as part of an active scan session. These local files are removed when that scan session is discarded or replaced.
3. OpenAI
Mineral Signal uses OpenAI to analyse images submitted through AI Scan Mode.
OpenAI may receive:
- the processed scan images
- mineral identification instructions
- specimen observations supplied as part of the scan
- reference information needed to perform the identification
We do not send your Mineral Signal account identifier, name, email address, authentication token or payment details to OpenAI as part of the scan request.
OpenAI processes this information to provide the AI identification service.
When we share user data with third-party service providers, we require them to provide the same or equivalent protection of that data as described in this Privacy Policy and as required by applicable law.
4. DeviceCheck and free scans
Mineral Signal uses Apple DeviceCheck to help prevent repeated claims of the introductory free scans.
When eligibility for the free scans is checked, the app obtains a one-time DeviceCheck token from Apple and sends it to our server. Our server then communicates with Apple DeviceCheck.
We do not use DeviceCheck as an advertising identifier and we do not store the DeviceCheck token as a persistent device identifier.
We use DeviceCheck only for app functionality, security, and prevention of repeated promotional claims.
5. Purchases and subscriptions
Purchases and subscriptions are processed by Apple through the App Store.
Mineral Signal does not receive or store:
- credit card numbers
- bank account information
- Apple payment credentials
Our server does receive and store technical purchase information required to provide paid functionality, including information such as:
- Apple transaction identifiers
- original transaction identifiers
- product identifiers
- subscription status and dates
- purchase environment
- the Mineral Signal anonymous account associated with the purchase
This information is used to:
- grant Scan Pack credits
- grant subscription scan allowances
- verify subscription status
- prevent duplicate credit grants
- support Restore Purchases
6. Data stored by Mineral Signal
Depending on how you use the app, Mineral Signal may store:
- anonymous account identifier
- hashed authentication token
- scan request records
- cryptographic image fingerprints
- mineral identification results
- scan credit balances and credit history
- complimentary scan eligibility records
- Apple purchase and subscription identifiers
- subscription and Restore Purchases records
Production scan images themselves are not stored in the Mineral Signal database.
7. Logging
Our production server may create technical logs required to operate and troubleshoot the service.
These logs may contain technical information such as:
- anonymous account identifiers
- scan request identifiers
- Apple transaction identifiers
- model and request information
- scan metadata
- identification results
The production application is not designed to write submitted scan image files into these logs.
8. Analytics, advertising and tracking
The current version of Mineral Signal does not contain third-party advertising SDKs.
We do not use your data for:
- third-party advertising
- targeted advertising
- cross-app or cross-website tracking
- advertising measurement
- marketing profiling
The current version of Mineral Signal also does not use a third-party analytics or crash-reporting SDK.
We do not access Apple's advertising identifier (IDFA) for tracking purposes.
9. Data retention
Different types of information are retained for different periods.
Scan images processed by our production server are not stored as persistent image files in our database.
Some information, including scan records, image fingerprints, credit records, anonymous account records and purchase/subscription records, does not currently have an automatic expiration period in the application.
Local scan-session images may remain on your device until the active scan session is discarded or replaced.
Where a third-party service such as Apple or OpenAI processes information, its own retention and data-processing rules may also apply.
10. Data deletion requests
You can delete your Mineral Signal account from inside the app (Plans & Scans → Delete Account).
When you confirm, we delete that account and the personal data stored with it, including scan identification results, scan credits on that account, and sign-in tokens. We do not keep a Mineral Signal user account record for the deleted account.
We may keep a minimal App Store integrity record that is no longer linked to the deleted Mineral Signal account. This may include Apple transaction identifiers used to prevent the same Scan Pack purchase from being credited twice, subscription-chain state, and a record that a subscription allowance period was already opened so the same period cannot be granted twice.
These retained records are used for purchase and subscription integrity, not to maintain a profile of the deleted user.
Unused Scan Pack credits on the deleted account are not transferred to a later account.
Complimentary scans are granted once per device and are not granted again after account deletion.
If you still have an active Apple subscription, you can use Restore Purchases after Mineral Signal creates a new anonymous account.
You may contact us at info@stefanskristallen.nl if you have questions about this Privacy Policy or a deletion request.
11. Third-party services and infrastructure
Mineral Signal uses external services as part of its operation.
Apple
Used for App Store purchases, subscriptions, Restore Purchases and DeviceCheck.
OpenAI
Used to analyse specimen photographs submitted through AI Scan Mode.
Railway
Used to host the Mineral Signal production backend and related server infrastructure.
12. Children's privacy
Mineral Signal is intended for a general audience and is not specifically directed at children.
The app does not require users to provide their name, email address or other direct profile information.
We do not use information collected through Mineral Signal for advertising or tracking children or other users.
13. Changes to this Privacy Policy
We may update this Privacy Policy when Mineral Signal changes, when new features are introduced, or when legal or technical requirements change.
The date at the top of this page indicates when this Privacy Policy was last updated.
14. Contact
For questions about this Privacy Policy or to make a privacy or data deletion request, contact: