Indian Stone (Indian Black Granite for Precision Measuring Tools / Imported Gabbro) Main Composition
The Indian Stone used in the industry for marble/granite inspection platforms and CMM bases is essentially a fine-grained gabbro to diorite, often classified as a dark-colored basic intrusive rock.
I. Main Mineral Composition (Percentage)
Plagioclase: 55%–65% (Primary)
Calcium-sodium plagioclase, tabular crystals, determining the stone’s dense structure, high hardness, and minimal deformation.
Pyroxene (Common Pyroxene): 25%–35%
Dark mineral, constituting the base black color, enhancing density and rigidity.
Biotite: 3%–8%
Flaky dark mineral, distributed in small quantities, affecting polishing and color.
Olivine, Magnetite, Ilmenite: Trace amounts
Increasing density and light absorption, resulting in the Indian Stone’s pure black color with few white spots.
II. Chemical Composition (Main Oxide Ranges)
SiO₂ Silica: 48%–52% (Basic rock, relatively low silicon content)
Al₂O₃ Aluminum Oxide: 15%–18%
CaO Calcium Oxide: 8%–11%
MgO Magnesium Oxide: 6%–9%
FeO Fe₂O₃ Total Iron: 8%–12%
Na₂O, K₂O: 2%–4% Trace alkali metals
III. Core Property Correlation (Why Suitable for Precision Platforms)
Fine-grained, uniform, and densely crystallized mineral particles
Structure free of porosity and cracks, with low internal stress
Low coefficient of thermal expansion, extremely low water absorption, and resistance to deformation
Excellent mirror finish after polishing, pure black base color with very few white impurities, more uniform than Zhangqiu Stone and Northeast materials
IV. Simple Composition Distinction from Jinan Black
Jinan Black: Also a gabbro, primarily plagioclase pyroxene, higher density, finer crystals, and stronger stability;
Indian Stone: Similar composition with slightly different mineral ratios, overall performance close to Jinan Black, with a higher cost-performance ratio.
