Physical Address
304 North Cardinal St.
Dorchester Center, MA 02124
D2131-22 – Standard Test Method Technical Guide
📐 Scope and Size Classification
This standard, designated D2131-22, provides a classification system for natural muscovite mica splittings. It covers the determination of standard commercial grades and specifies the maximum allowable physical defects for each grade. The classification applies to all commercially available natural muscovite mica splittings, regardless of their basic color or source. The values stated in inch-pound units are to be regarded as the standard.
Thirteen specific grades, based on size and form, are described within the standard. These size requirements are detailed in Table 1 of the standard and must be used in conjunction with Classification D351, which more completely defines the areas and minimum dimensions that constitute the size grades. Within these grades, up to thirteen categories of visual quality can be specified.
🎯 Visual Quality Categories
The visual quality of mica splittings is a key classification parameter. Drawing from Classification D351, the standard defines multiple categories that range from perfectly clear to heavily stained. This ensures that the material procured meets the specific aesthetic and functional requirements of the application. Not all visual quality categories are available in all grade sizes, which helps keep the classification system practical and aligned with market availability.
| 🟦 Category | 📏 Description |
|---|---|
| V-1 | Clear |
| V-2 | Clear and Slightly Stained |
| V-3 | Fair Stained |
| V-4 | Good Stained |
| V-5 | Stained A Quality |
| V-5.1 | Stained D351 Quality |
| V-6 | Stained B Quality |
| V-7 | Heavy Stained |
💡 ISO Correspondence: ASTM D2131 is very similar to ISO 6386. The “ASTM Grade No.” in Table 1 and Table 2 corresponds to the “Old Grade No.” in ISO 6386-1981. Materials are expected to be classified identically using the criteria of either standard.
⚙️ Physical Properties and Defect Limits
The standard enforces strict tolerances on physical defects to ensure uniformity and reliability. Splittings must meet the size requirements specified in the standard’s tables, and total defects are strictly controlled. The distribution of defects is evaluated holistically to ensure no single category is overrepresented.
| 🎯 Requirements Category | ⚡ Specification |
|---|---|
| Total Defects | Maximum allowable total defects as specified in Table 2, calculated as a percentage by weight. |
| Defect Distribution | Defects must not lie predominantly in any one category. |
| Single Defect Limit | No single defect type shall exceed the specific percentage weight allowance provided in Table 2. |
| Foreign Matter | Foreign matter is strictly prohibited among the splittings. |
📌 Strict Compliance Required: The standard explicitly prohibits the inclusion of any foreign matter. Tolerance for defects is not a composite allowance for a single flaw; the distribution of defects must be balanced across categories as defined in the detailed tables of the standard.
❓ Frequently Asked Questions
© 2026 TNLab — This article is a technical interpretation for reference only. The original standard as published by ASTM International takes precedence.