A touchstone is a physical reference specimen — originally a dark siliceous stone (basanite) — against which samples of precious metal are rubbed to produce a streak whose color is compared with streaks from standards of known purity, thereby determining the metal's alloy composition. The concept persists through two mechanisms: (1) the literal practice of assaying in metallurgy and jewelry, governed by standardized test procedures and institutional calibration; and (2) the metaphorical extension, where any established benchmark or accepted criterion serves as a touchstone for evaluating non-metallic things — arguments, art, standards, relationships. Parameters: (a) the original sense requires a physical stone of appropriate hardness and texture, a sample of unknown purity, and comparison standards of known composition; (b) the metaphorical sense requires an established benchmark recognized by a community of judges. [formal: touchstone | substrate: behavior | horizon: a life | explicit: yes | epoch: 0.01]
Accepted ontology entry
touchstone
A touchstone is a physical reference specimen — originally a dark siliceous stone (basanite) — against which samples of precious metal are rubbed to produce a streak whose color is compared with streaks from standards of known purity, ther…
Definition
Why it is in scope
A physical reference specimen — originally a dark siliceous stone — used to test the purity of precious metals by the color of the streak it produces when rubbed; by extension, any established benchmark or criterion used to judge quality, authenticity, or value. Human-made as both a concrete assaying practice and a metaphorical standard; built to persist through metallurgical tradition and continued use as a judgment criterion.
Names and aliases
- touchstoneen · CANONICAL
Relations from this entry
- cmr98h9fl008khcxfwebiv8rnINSTANCE_OF →
A touchstone is a specific kind of tool — a physical artifact (fine-grained stone) used to extend human metal-testing capability. The competent-speaker test passes: 'a touchstone is a tool.' The definition carves it as both the original assay object and the metaphorical benchmark, both instances of the broader tool concept. No intermediate kind exists between touchstone and tool in the accepted graph.
- cmr9u6cjb00cyhcxf565q5jsrINSTANCE_OF →
touchstone is a specific kind of standard — a criterion used to evaluate quality or authenticity. Competent-speaker test: 'a touchstone is a type of standard.' Direction: specific (touchstone) → general (standard). Epoch test: touchstone is older, which is fine for INSTANCE_OF (unlike DERIVED_FROM — which-came-first doesn't govern kind-of relations).
- cmrnaoqvi0227d1nlvj8ojuxzINSTANCE_OF →
A touchstone is a standard or criterion by which something is judged or evaluated. Clean specific→general INSTANCE_OF.
- cmrvj9i7x01c72ceipxppg8h0SERVES →
touchstone is used as a standard for evaluation
Relations to this entry
No accepted relations in this direction.
Record identity
- Created
- Jul 30, 2026, 6:23 AM UTC
- Content hash
- 7f59ee8886c30a163d0d2c91bec144a56ff62918a3faf345f8bcb24af1b725b9